It's not just some "rich dude". The highest bidder [1] (so far) is Justin Sun, creator of TRON crypto [2]. I see this as a big publicity stunt for his personal branding.

Not too different than paying $4.5M to have a dinner with Warren Buffett [3].

[1] https://www.coindesk.com/twitter-ceo-jack-dorsey-is-offering...

[2] https://en.wikipedia.org/wiki/Justin_Sun

[3] https://www.coindesk.com/trons-justin-sun-finally-gets-4-5m-...