He could just give them money for it. I'm sure they'd love having a multibillion dollar customer.
It's very possible that his AI investments have yielded developments that we can't imagine. But it's hard to see the value of twitter's data over that of, say, the internet cache that gpt-3 uses.
Sure he could pay for it, but buying the company (and taking it private) is potentially a way to get paid for access. Web archives - like common crawl - are snap shots of the past, but twitter users react and discuss events in real time.
Reliably parsing and interpreting new, potentially unreliable data is part of that whole AI-complete thing.
It's very possible that his AI investments have yielded developments that we can't imagine. But it's hard to see the value of twitter's data over that of, say, the internet cache that gpt-3 uses.
I have no idea what the plan b he alluded to is.