There are 7 to 8 million military age men willing to fight to the death for the current government. Any CIA created “government in exile” or boots on the ground would be recognized as the enemy and fought as a attritional war, dragging out over decades. (see Vietnam, Afghanistan, Iraq and on and on). That’s why we don’t do it I’m guessing.
Vietnam, Afghanistan and Iraq turned into generational wars not because we couldn’t have won them, but rather because we were not prepared to do what was necessary to win.
In Afghanistan and Iraq, the core problem ultimately was Iran, and we were never willing to do the necessary. That was apparently seriously discussed in the Bush administration at the time, but the dems had conniption fits and the support in Congress would have been lacking.
Bush was followed by Obama, who did his groveling tour and basically went pro-mullah.
There is a long precedent for what Trump is doing now. It has become the American Way of War. Start something we’re not prepared to finish and hope we get lucky.
Every potential adversary knows this. And they all know the democrats will become a fifth column the moment a Republican is in the White House. Outlast the Americans is on the first page of the official bad guy handbook.