As the server source drop showed, they had been working on it since April 2020, publicly downplayed the idea just three months ago, and then... launched the beta. I would describe that as pretty deceptive.

"Marlinspike played down the potential of crypto payments in Signal, saying only that the company had done some “design explorations” around the idea. But significant engineering resources have been devoted to developing MobileCoin integrations in recent quarters, former employees said."

January 25th, 2021

https://www.theverge.com/22249391/signal-app-abuse-messaging...