Viewed in light of this it seems likely they wanted to cement control of Telegram and the founder refused their advances.
It's not enough for the US to be able to utilize a thing for their ends, they desire the ability to deny their enemies the same (which flies in the face of the liberal notion of freedom of speech not just for who you like but those you dislike). As well as probably wanting technical data and backdoors to identify both puppets and pawns as well as enemy groups they can target for surveillance, harassment, arrest, deplatforming, etc.
In light of these kinds of tactics one has to look at something like Tor with a skeptical eye. Maybe it was just made before all this was common practice. But I personally find those whisperings about the idea that 90% of exit nodes and other parts of the network are run by isnt'reali, US, and eyes intelligence agencies to allow de-anonymization on anyone but their people using it.
Anyway you look at it, this, the raid of Scott Ritter as well as the home of another RT host whose last hat was writing for a Nixonian realist conservative policy magazine, among many other actions and it seems the boot is coming down hard and fast. That is that the US firewall is being erected but unlike China's which seeks merely to control their own information space, the US is clamping down hard on anyone but them speaking or coordinating, organizing, putting forth opinions. They're no doubt incensed by the amount of conservatives in the US who view Russia sympathetically. The deranged agents of the FBI and so on who fully bought into the de-bunked Russia-gate hoax clearly see any sympathy as evidence of Russian meddling and the larger strategy moving above and beyond them of the state is to crush movements against its interests now.
From crushing Palestinian genocide protestors (and going so far as to punish the proles by banning medical face masks) to this they're reaching out to crush and achieve total dominance on all fronts for all their narratives from their settler-colonial genocide-state isn'treal to the Russian antagonism, to China and beyond. That's why we see a resurgence in pushing the Xinjiang genocide lie again as well I think.
And it's why Tiktok was banned, why Kaspersky was banned (not sharing data with the NSA like US AV firms do), and why they're now harassing this Telegram guy.