Let’s be fair: “I was wrong about the bad nature of somebody else” is pretty much the lowest, mildest, weakest possible form of self-criticism there is, to the point that it’s quite common for posh manipulator types to use “I was wrong about your ,<proceeds to criticized the other person>” format of discourse to criticize others.
One would expect that any competent national leader would’ve requested an intelligence folder about Trum,p at the lastest when he was elected POTUS, and this being Germany, they have the capability to produce one which is very complete and beyond what we common mortals can deduce about the man’s nature.
Whilst a politician in such a high position in a country isn’t necessarilly more capable of analysing things than a common mortal (though it’s logical to expect they’re significantly better at judging people than most, since that’s a requirement in their profession and to reach such a high position they must be top performers at it), they most certainly have access to much better and deeper information than any of us and to people who can do the analysing for them.