[shoemakersteve]

Just barely. Had the military been just a bit more indoctrinated, they may have started shooting. Which, as far as I understand, were the instructions they received. If nothing else, if the legislators weren't able to get in, this would have gone a whole other way, and the coup could easily have been successful.

[ANewFormation]

It's not about military indoctrination but the popularity of the leader. Yoon is exceptionally unpopular. If he had 80% approval, instead, he would probably now be the dictator of The People's Democratic Republic of South Korea.

Without that approval the best you're looking at (from his perspective) is mass unrest which an opportunistic nation like their neighbor could foment, support, and exploit.

[michaelt]

If you've got 80% support in a democracy you don't need to declare martial law and overthrow the legislature: If you're that popular your party will easily secure a sizeable majority in the legislature and you can pass any law you want.

[suraci]

In fact, DPRK anticipated that Yoon Suk-yeol might attempt to ignite conflict on the peninsula to justify imposing martial law. Therefore, DPRK preemptively severed the roads between the two countries to prevent this from happening. Although DPRK is often scorned by the West, it is far more rational and stable than many other countries.

https://www.bbc.com/news/videos/c70wgxr4zndo

[oefrha]

He’s just too incompetent, utterly failed Military Coup 101:

1. Cut communications;

2. Make sure the troops you send to capture critical objectives are hardcore loyalists (or at least paid exceedingly well).