I think they've counted on the Ukrainian government (especially Zelensky and his closest circle) to give up the fighting and surrender early in the operation. Or have Ukrainian army overthrow him, Putin already suggested they don't need to take commands from this "narc" and "nazi" (btw Zelensky is jewish). It's either their intelligence is that bad (which I don't believe) or Putin just didn't listen, having some delusional picture of the current political and cultural state of Ukraine in his head.
They're completely different. Both are evil, but Putin is extremely clever, which makes him a lot more dangerous than Trump. Trump can't do much more aside speaking to people bellies; surely he can amass lots of uneducated angry proud boys around him, but has zero credibility among the high ranks in the military.