It doesn't surprise me at all that Trump admires Gaddafi and Saddam - Trump is just another dictator in waiting and the US populus may well be dumb enough to put him in power. Getting him out will be tricky.
For very small values of "rational". What is a valid point is that it is much easier to create a failed state than to rebuild from the ashes.
We went into Iraq because Dubya wanted to "kick some Arab ass" and he couldn't attack Saudi Arabia despite the fact that almost all the 9/11 terrorists and most of the money behind it came from there.
We had absolutely no plan about what to do after we had "won" the war.
It is interesting to note that British intelligence reports during the WWI era accurately predicted the outcome of invading Afghanistan over a century earlier. Those that do not know history are doomed to repeat it.
The Russians tried and failed a few decades ago and they are not quite so squeamish about human rights. Mountainous places are hard to invade. More so when they have porous borders and hostile (to us) neighbbours.