Telegram has like 30 people and is more feature rich, faster in development, smoother in operation and the stuff they provide is more mind-blowing than whatever Meta's team has ever come up with.
But most of all, it was created much much later, after all the patterns and techniques have already being ironed out by the first wave of chat systems.
I don't see how that has an edge over the cloud sync functionality though.
Cloud sync, having thousands and millions of people in a group, group topics, 4GB file sending limit are more impressive than some closed source implementation of E2EE we can never even verify.
> all the java phones whatsapp does ( not sure if whatsapp still do though).
It doesn't anymore.
Telegram works even without an app, through their website (On phones too, yes) so I'd say it's more accessible and having open source clients and APIs means that you can create a Telegram client for literally any platform.
This is, imho what makes whatsapp uniquely hard to scale.