There is nothing unreasonable here, it's perfectly understandable. Stock market crashed, which means the proposed buying price for Twitter is now too high, PLUS

There is nothing unreasonable here, it's perfectly understandable. Stock market crashed, which means the proposed buying price for Twitter is now too high, PLUS Tesla stock is less valuable which means he has to use a lot more to get funding. It up debatable whether he wants out of the deal completely or just want to negotiate for a lower price though.