Telegram is ostensibly a competitor if you buy into Musk's pitch for X as an "everything app". Paying Telegram $300M instead of developing chat features and/or marketing proves that plans for the "everything app" are dead in the water, or perhaps were never sincere from the get go.
It's honestly a good fit. Telegram also doesn't have the best image, but people don't care, so it's highly likely that they also don't care about the image of XAI or Musk.
I do struggle with the 1 billion users, but I also don't believe that X has 600 million users actual users.