As someone who has been into cards and collectibles all my life, the past few years have been wild to say the least.
What we saw in 2020/early 2021 was really a classic bubble - FOMO buying pushing prices to unsustainable levels. Then throw in the grading shutdown caused by backlog of new collectors and investors sending in millions of garbage base cards for grading, clogging up the grading companies, plus profit taking from the insane prices, and we get the pullback we saw in Q2.
Like everything else, the collectible market comes down to supply and demand. Focus on rare cards - numbered cards, colored paralells, refractors etc…the supply is much lower and are generally safer bets because collectors are always chasing them.