Iran brutally slaughtered its protestors. Up to 20,000 were killed.
Iran’s revolutionary guards are stronger than its regular military and they are loyal to the supreme leader.
Trump literally said that “help is on its way”, and many protesters said they expected Trump to help. When he didn’t, the ones that were still alive, felt betrayed.
A US intervention would likely cause a retaliatory strike, and the US wasn’t prepared for such attacks because it was using resources around Venezuela.
Local partner countries warned against a US intervention, fearing a regional conflict.