Can you explain why the collateral required is higher (if no one has any insolvency issues)?

If you watch the video I posted in the parent comment with the webull ceo, he states the exact scenario where brokers have no problem margin calling a small retail account, but for a big firm and big losses it's problematic, and so do you have more to add than the webull ceo on this topic?

I encourage the discussion and the information you added. Prime brokerages may be able to absorb the damage and thus are able to post the collateral needed, but then if the smaller brokerages like robinhood also need to post the same collateral while having smaller risk of clearing problems, isn't that the problem of the risk spreading?