On media influencing decision-making, you might want to give Giulia Buccione and Marcela Mello's working paper "Religious Media, Conversion and its Socio-Economic Consequences: The Rise of Pentecostals in Brazil" a read.
I do work in this academic neighborhood, so maybe I’ll comment a bit. There’s a part of me that feels like caricaturing Linch’s question as akin to asking: What were all the other physicists doing with their time in 1905, when Einstein was sitting around churning out paradigm-shifting papers without a PhD or even access to a decent academic library? But that’s probably unhelpful, so I’ll try to give a bit more color on Kremer’s context.
First, it’s important to understand that until very recently, experimental work in LMIC settings was really prohibitively difficult to 1) organize and 2) get funded. Prior to the founding and (recently explosive) growth of the J-PAL/IPA network (in which Kremer himself played no small part), as well as the emergence of the Gates Foundation as a major funder of global health RCTs, these studies were just really, really hard to do. Moreover, even if you could put one together, until the last 10-15 years, you were very unlikely to be able to publish your results in a top-5 economics journal (and top-10 economics departments assess their tenure-track faculty almost exclusively on the basis of their publications in top-5 economics journals). If you look at Duflo’s early work on healthcare in India, a lot of it published, well, badly, by the standards of the MIT Economics Department. Miguel & Kremer's original deworming paper did make a top-5 journal (Econometrica), but only because they spun their contribution as principally methodological in nature. The title is “Worms: Identifying Impacts on Education and Health in the Presence of Treatment Externalities;” the paper basically pretends to be about approaches to accounting for potential interference/spillovers between treated and untreated units in an experiment, rather than about deworming itself. I’m too young, but folks I know who were around those circles at the time recall being told that empirical research on health in LMICs “wasn’t economics,” that it was “just reduced-form” and that committing to it was a terrible professional decision. This assessment of the professional consequences wasn’t without justification, either. Seema Jayachandran was denied tenure at Stanford as recently as 2011 due to prejudice against this sort of research. What Banerjee, Duflo, and Kremer won the Nobel for, more than anything else, was changing the field’s conception of what counts as economics in a fairly dramatic way.
So how did folks like Banerjee, Duflo, Kremer, Karlan, Miguel, etc. overcome those obstacles? In the cases of Banerjee and Kremer, both had established themselves as theorists (and received tenure at MIT) before they turned to doing experimental work. In the cases of Duflo, Karlan, and Miguel, 1) they were Banerjee/Kremer students, so they had access to that source of encouragement and support, and 2) they were unusually principled about their interests and willing to take gigantic professional risks.
The consequence of this is that those five names—in one permutation or another—are on a huge proportion of the papers evaluating health & development interventions with credible identification that were published prior to ~2010, and as for interventions that were first evaluated more recently, well, 1) the evidence base about those interventions is often still too thin to be the basis of a GiveWell recommendation, and 2) running these RCTs may be easier today than it was 20 years ago, but it’s still administratively challenging and (more importantly) difficult to fund. If you’re going to persuade Gates (or someone similar) to give you a seven- (or eight-) figure sum of money to figure out if sending people text messages gets them to vaccinate their children, it really helps if you can say that you’ll be drawing on someone like Michael Kremer’s network and expertise in putting your study together. This isn’t just empty signaling, either. There’s a lot that can go wrong in organizing an RCT like this, and having someone on the study team who has loads of experience navigating the challenges that tend to arise is genuinely very valuable. Moreover, if you’re a junior researcher, you may need someone like Kremer’s network in order to get the approvals you need to launch your intervention from the government wherever you’re working, to access J-PAL/IPA resources in-country, and to connect with other reliable implementation partners on the ground (e.g., local non-profits, survey firms, etc.).
In conjunction with the fact that Banerjee, Duflo, Kremer, Karlan, Miguel have all skyrocketed to (global) prominence in the last 15 years, this means that much of the best (particularly experimental) work happening in health and development even today still has one of their names on it. The best work, after all, requires a lot of money and excellent contacts, and the distinguished stature of those five economists has left them with money and contacts in spades. If you go on Kremer’s lab’s website, you can see that it employs, like, a shocking number of people (for a social science research center in a university setting). His personal contribution to the clean water paper under discussion here was probably not enormous, but it’s nonetheless no coincidence that he led it. If I’m a promising young economist with ambitions to do impactful work on these topics, then Kremer is going to be among the people I’d be most eager to collaborate with; I'm going to do everything I can to build a working relationship with him (especially given that he is also, reputedly, a nice guy). I think that's why you see him behind so many of GiveWell's recs.
And this isn't even to mention Kremer's substantial contributions to growth theory (which are still his second- and third-most-cited papers), much less the major theoretical contribution he made to the modeling of HIV transmission in his free time back in the late 1990s...
It's worth noting that the second of those papers actually has recently been reanalyzed, and Cutler and Miller have now published a response to the reanalysis, as well. I think there is probably more work one could do on this (e.g., updating the difference-in-differences estimators in the original paper to reflect the current methodological state-of-the-art), but I also think it's fair to say that the result has already been subjected to thorough and meaningful scrutiny.
The political scientist Yuen Yuen Ang has some great work addressing this neighborhood of intuitions. Her view is basically that “corruption” is decomposable into a several distinct types of phenomena, and some of these can be growth-promoting (as in China during the period between, approximately, Deng and Hu), whereas others can be fairly extreme impediments to growth.
If you’re serious about pursuing a master’s in economics, it might make sense for us to chat — I know a bit about those programs (in the U.S. context). Depending on where you went to undergrad, what courses you took, your GRE scores, and whether you can spin a compelling narrative about why you finished with a 2.95 GPA, you may be able to get into decent master’s programs without any post-bacc coursework. I know folks who’ve done so with similar grades. That doesn’t mean, of course, that heading off in that direction would be a good idea, but it may be more of a live option than you think.
On this topic, Desmond Ang's recent AER paper “The Birth of a Nation: Media and Racial Hate” is also worth a look.