No matter how much I consider Trump a dimwit liar, I can't completely shake off the other explanation, that of yesmen telling him whatever they thought he would like to hear. I suspect that in a position like that, even making up falsehoods is conveniently delegated. You don't lie, you just select convenient sources to parrot. Putin must have spent recent years in an even worse yesmen-bubble, the shift from him being considered dangerously competent to him being considered dangerously senile should really not come as surprising as it does.