It’s a big pie, they’re also fairly different. And to be honest it’s only a matter of time before Telegram has a (public) security incident that drives much more people to E2EE messaging.
I'm curious how long it will be before that public incident - they rolled their own cryptography right? With that, I would imagine that if it hasn't been pwned yet, then there would be a disproportionate amount of people trying to break it.