A lot of different strings to pull on this one.
1) For the most part, I don't believe there is a ton of market manipulation, just crazy irrational exuberance. Yes, it's very hard for any of these cards to retain their value over time. A lot of time it's just straight up gambling.
Take a look at this example:
https://www.blowoutforums.com/showthread.php?t=1542293
Hundreds of different collectors paying hundreds or thousands to get a specific card lot in a break of 100 cases of Bowman Chrome Draft. 95% of those slots will be money losers, with people spending $86 to get $5 worth of cards on the open market in a couple of weeks. And this is completely honest and open, no market manipulation. There just is that much demand for modern prospect cards.
2) Some of the manufacturers seem to be tipping their hands by serial numbering certain boxes within cases and leading breakers to find ones that are "hot" or containing a rare hit. If the boxes in a case are numbered 6,888, 6,889, 6,890, 6,891, 6,892, and 3,503, it's easy to spot the odd man out and determine there's probably something valuable in 3503.
3) Cards like the Kris Bryant 1/1 Superfractor Auto from 2013 Bowman Chrome, which went for $50K or so at its peak, is probably worth $10K or so right now, and Bryant has actually had a pretty good career.
Take a look at this thread if you want to ride a wave of emotions:
https://www.blowoutforums.com/showthread.php?t=860461