I dont get how The 1st dude (the 2008 short guy) can pretend their is a systematic risk

Here's the important bit from Michael Burry:

“Potentially making it worse will be the impossibility of unwinding the derivatives and naked buy/sell strategies used to help so many of these funds pseudo-match flows and prices each and every day.

There's liquidity you want and there's liquidity you need. If you would like to sell a million shares of Alphabet, there's probably a buyer for a million shares of Alphabet. However, if you need to sell a thousand shares of Alphabet because you need to rebalance your ETF at the end of the day, you can't really wait. And you take whatever price you can get. In a market where 99 big fuckin' ETFs are doing the same thing you are and another 100 or so that still gotta dump. Of the 1700 ETFs in the United States, 200 of them hold GOOG. So in a big market move, GOOG is going to move. And considering the CU holders have minimal financial incentive to get the best price, they're going to dump it when they need to dump it.

Not everybody needs to sell to shitcan the price. If a million people hang onto their shares and a thousand people let it go for 50 cents on the dollar, the market cap held by that million people goes down just the same.

And if GOOG goes down, every fund that holds GOOG has to sell everything else in their fund to rebalance. So. Bad day for Google, ten percent of the ETFs on the market are selling.

THAT is what Burry means by "the impossibility of unwinding the derivatives" and "naked buy/sell strategies... to match flows and prices." It's like a short squeeze - you need to cover the short. And if there's no stock to cover the short, you pay whatever you need to cover the short.