Thanks for this post! It's an interesting perspective on some factors that might explain the coup. I'd just like to add a couple of things worth considering, based on what I know. I'm not very certain about how these factors interact with what you've written above. 

(a) Personalities. A lot of the military's decisions seem to stem from the personality and ambition of the top leader at the time. The military leader who initiated the shift to democratization in 2009/2010, Than Shwe, was sort of a wildcard and even military insiders were a little taken aback by his decision to democratize. Sanctions had something to do with it, but it's far from clear that they were straightforwardly the impetus for the democratic transition. His successor of sorts, Thein Sein, proved to be much more moderate and reformist than almost anybody expected. The current military leader, Senior General  Min Aung Hlaing, has not been shy about his ambitions to be President and has previously extended his reign on power past the mandatory retirement age to get the chance to be President of Myanmar. He was set to retire from the military after this last election and could have then been nominated by the military to be Aung San Suu Kyi's vice president (there are two vice-presidents, one always nominated by the military). He's reported to have hated the idea of working in a subordinate position to Aung San Suu Kyi. 

(b) Ongoing Civil Wars. While the country did democratize in 2010, many parts of the country have been undergoing civil wars of various types for several decades. The military is active and present throughout the country, controlling territory in part through official brigades, allied militias, and peace agreements with ethnic minority armed groups. I think the NLD's power to frustrate military power and interests is limited and even after repeated electoral defeats, what probably would have been damaged is the military's pride rather than its actual hold on power.

In any case, these are just some thoughts off the top of my head.  Sadly, whatever's happening in the country is a tragedy and will likely set back a decade or more of development efforts.

Source: a Myanmar politics class and my own Myanmar studies research work (sorry I don't have any links on-hand) 

Hi David, thanks for your comment! The source you've linked looks really interesting and relevant. I'd be happy to speak to you sometime next week. Could you book a slot here? https://calendly.com/mss74/30min

Thank you for your comment and this reference! I wasn't aware of this group. I've edited the post to include them!! 

No worries, glad it was useful. Thought I would update that we've put all that information into a website with somewhat regularly updated summaries of the pandemic responses in the various Southeast Asian countries: www.regionalrelief.org

Thank you for laying out your thinking on this topic! Was hoping to find something like this. Since you mentioned Southeast Asia I thought to link to something I've been working on - a compilation of Southeast Asian charities/organisations working on COVID Relief. https://docs.google.com/document/d/137XQpOwjPIcVhV1oufK83zHB64SKMAXtFg9YjPYe76s/edit

Some caveats: Not sure how interesting it would be, it's been quite a challenge to find these charities/orgs as is, and I have not had the bandwidth to evaluate them systematically. I've also only listed organisations working directly on PPE Provision or giving Supplies to the Vulnerable because a small 50person survey I did suggested that generally people are more likely to donate to short-term relief efforts than long-term capacity building. My main aim is to encourage richer Southeast Asians to give some money to parts of the region where the needs are clearly more pressing. I will be trying to analyse them the way you guys have done at a future point, but currently my aim is to just get more attention in places like Singapore/Malaysia directed towards Indonesia/Myanmar/Philippines through a digital donation campaign.