I got back into collecting in March 2020. Not because I thought there was a great investment opportunity, but because I all of a sudden decided I needed Mattingly rookies I couldn't afford as a kid. Trapped at home I took comfort in the nostalgia of cards.
After securing every card I had when I was a kid (primarily rookies from Dale Murphy - Roger Clemens), I turned to vintage. I went in heavy and overpaid most likely (at least in Aug/Sep), but am glad I did. I was able to get a handful of really special cards (Gehrig, DiMaggio, Robinson), but watched the Cobbs of the world gradually pick up enough speed that now there's no chance. I always say I'm going to buy something and sell it to buy something else, but can't stand the thought of selling.
I troll the BST threads/auction houses, but for now I'm back to building a Mattingly Master set. It's the fun of the chase with a budget that my wife won't leave me over.
For the bubble to pop, people like me need to stop buying so many cards. That isn't going to happen (for me at least).