The assessment that Putin is "smart" by exploiting an internal dispute in Ukraine in order to invade it is weird on its own merits. Firstly, because it's pretty obvious that "smart" Putin expected this to be over already; secondly, because it's not even remotely an original tactic; and thirdly, because more or less everybody who was paying even the slightest attention could see this invasion coming a mile off.
So the main problem with what Turmp said about Putin is that it's just wrong. This isn't smart at all. It's page one from the "make up a fake casus belli" rulebook.
As to the assertion that Trump's presence in the White House would have seen this never happen -- well, I can only point people to, for example, the Turkish attack on the Kurds, which Erdogan started after calling Trump and persuading him in approximately a single phone call that, despite historic alliances between Kurds and Western countries, it wasn't his fight. It would have taken one phone call from Putin, and just a small amount of flattery, to get de facto permission for this.
It also doesn't do to blame Western Leaders' "weakness" for encouraging this. NATO was never going to intervene militarily directly, since to do so would be tantamount to a state of War between Russia and NATO countries; and, despite the huge show of support, continues to refuse to intervene directly. I do not condemn this position, by the way, but the point is that this position would have been true regardless of who was in office in the US.