It was a coup with extensive pre-planning and placement of pro-coup officials. In the lame duck period, Trump purged the Pentagon, AG and Defense Department, among others. Trump installed loyalists willing to bend/break rules that even Bill Barr wouldn't touch. Fucking Devin Nunes toady, and all around shitheel, Kash Patel was the Secretary of Defense's Chief of Staff. The new Secretary of Defense who took direct control of the D.C. National Guard, but only for January 5th and 6th. While the situation escalated, the National Guard was held up for critical hours before finally deploying. Mike Flynn's brother Charles helped delay the deployment
https://www.esquire.com/news-politics/politics/a38439573/january-6-national-guard-delayed-trump-pentagon-officials/
If Pelosi had accepted 10,000 troops, they would have been under the leadership of pro-Trump and pro-coup zealots. I don't know what would have happened, but the odds of something even more catastrophic happening would have been fairly high.