Testing the waters, I guess.

"it's my birthday today [AI generated image of Grandma with birthday cake]" is a viable business model on Facebook these days: https://www.404media.co/where-facebooks-ai-slop-comes-from/

If they get enough clicks they could put profitable ads on the page, or even sell it (like what happened with Wordle).

Go viral and show ads?

Get the chatter going, get "press", clicks, visitors and players, then potentially ads, or selling the site (for someone else to put even more ads on it), or using it as marketing reference (I made a game viral by lying about it).

Wordle sold for $1+ million. An average word game with a unique hook like "my grandma made it" is well positioned to sell or at least attract a lot of viral traffic.

Anyway, the grandma story has been exposed as fake.