Why do some firms disappear?

Because they try to impress traders with unsustainable rules. They let cowboys go full-port with no risk management, paid out big early to look legit, then can't cover when the market shifts and luck explodes.

Firms with real rules aren't punishing you. They're staying solvent so they can pay the traders who do the work. A firm with no rules is a firm that won't be here in two years. Choose accordingly.