I mean, okay. But it's not like he had $44B in cash lying around.
Implicitly, this was always, "I'm going to trade X% of Tesla for 100% of Twitter." Then the valuation of both Twitter and Tesla dropped, so to the extent that you think the "value" of a business is wholly determined by its fundamentals, then okay, they're both still the same "value" but now have lower prices.
Except that he hadn't sold the Tesla yet, so he was trading Tesla (at new lower price) for Twitter (at old higher price), and if you previously thought that X% of Tesla was worth Twitter, and Twitter is still worth the same thing, it's now X+Y% of Tesla.
Of course, it's not like the fundamentals of Twitter didn't change. Twitter's revenue comes from advertising, and it's entirely reasonable to believe that it was actually materially affected by the economic downturn, not just in terms of the speculation of the stock, but by how the business functions.
(None of this is to take the position that Musk ought to be able to back out of the deal: if the market had gone even hotter and now Musk could've traded less than X% of Tesla for the agreed upon, now conservative price for Twitter, it's not like the deal would've been renegotiated.)