Then what happens? A messenger is only as good as the network of people on it. Signal already exists, and I have a few group chats on it, but most still happens on Whatsapp and FB-Messenger.
HNers will probably take VC money and sell to Meta eventually for a gazillion dollars. You should ask someone on the GNU mailing list (but they don’t have the time and money, especially marketing reach to compete with anything popular)