I always assumed it was because he believed the price he was paying was now too high anfter the tech downturn, and he wanted to try lower it a few billion. It’s roughly worth a few million in lawyer fees to take a 10% chance to lower the purchase price by just over a billion.

I think he was likely after a lower price than the impulsive one he offered

would you mind looking like a fool for a chance to save a couple billion dollars?

there's no fair market value for Twitter because there's only one Twitter. If you're rich, money is just a means to an end. you see something, you take it. If you think you can save a couple (billion) bucks on your way out, why not give it a shot? it's already yours