1) Pretty sure you're misinformed on this point. The hedge fund sector that has gotten attention and partial blame for this meltdown is the risk-parity segment of hedge funds. These funds target a specific range of volatility, so when the market becomes wildly volatile they are forced to reduce their overall holdings. The entire risk-parity segment of the market is at most $400bn and they are levered 2-3x on average. In the grand scheme of things, this is pennies when compared to broader money flow.
2) Stock buybacks are simply a more tax-efficient way of distributing profits to shareholders. Redistribution of profit to shareholders is a fundamental trait of capitalism, so you can't really blame the CEO for doing this. You seem to be blaming CEO's for not preparing for a black swan event. If CEO's are forced to prepare for every possible black swan event, their companies would go nowhere.