The past 30 or so years has been slow movement towards NATO so that if shit ever hit the fan, Finland could join pretty much immediately. This in conjuction with building self defense capabilities that would make an invasion - specifically by the Russian army - incredibly expensive.

In the end, the decisions to not join NATO and then to join were both done on national security grounds, and not for some sort of ideological stance. Finland's just shedding the remaining bits of finlandization now.