And it's not just a trademark matter. I haven't looked in detail at how the Twitter acquisition was structured, but somewhere there's a spreadsheet with the words "goodwill" and next to those words there's a huge number reflecting what Musk overpaid for Twitter.
To simply stop using the Twitter brand, logo, and verb-ology would be a huge slap to that number, not that it really means anything financially.
Unless the company forgets to renew the domain because everyone who would be responsible for that has quite or been fired. Not that I think this is at all likely, but God would it be hilarious.
Perhaps Musk will do something similar. He's definitely not going to give up Twitter, and even if he does, he'll keep the domain.