Finland is a good catch for Nato. They are not weasels or warmongers and are highly civilized- having extensive experience in honestly trying to avoid war and maintain relations with Russia the best they could, until they couldn't. Yes they have Russians in their population and some shared history there - but so do the whole pantload of former Warsaw Pact countries that are now Nato members.
Also, they are not freeloaders who avoided joining Nato just to save some bucks and then suddenly want to sign up when they feel threatened. Nope, they have maintained mllitary training and funding within their own country and have been sort of "associate members" of Nato in the sense that they train regularly with Nato forces even though they have remained non-members.
Putin went too far in threatening them. That was another big mistake on his part. He has ranted on about how he could not tolerate having Ukraine become a Nato member because he does not want another Nato member right on his border. Then Finland decides to join which -NO LIE- doubles the length of Nato border on Russia.
Idiot. The Finns don't bother anyone. They just do not want Russia rolling into their country again. The last time they did that the Finns fought them off in the Winter War. Nevertheless they lost a little chunk of Finland too. Yeh, they are not naive, they are well trained, and just want to be left alone. Nothing wrong with that.