It appears that the Binance move was a last-ditch effort to save FTX, which went from being a powerful player in the crypto market offering bailouts and looking to acquire bankrupt companies to an insolvent exchange struggling to stay afloat in an incredibly short period of time.
CZ of Binance hedged a bit in his announcement, underscoring that "Binance has the discretion to pull out from the deal at any time" and would be performing "full [due diligence]" before the deal moved forward. It's not yet clear how much the Binance sell-off of FTX tokens contributed to the instability of the exchange.