Telegram has more monthly active users than Twitter (400 million vs 360 million, according to Statista)
Even going by metrics like cultural significance, there are large regional differences. It's a little unfair to call them smaller, even if they don't quite have the same level of political and social clout in the US.
User numbers don't matter if you're not making money off them. Telegram is privately funded by Pavel Durov. Twitter's yearly revenue is equal to Durov's entire net work. Twitter's market cap is 250 times higher than Telegram's.
Durov's an extremely impressive individual. It doesn't change the fact that kicking Twitter off the app store could put a dent in Apple's iPhone sales and would almost certainly generate a lot of negative Western press. Telegram getting the boot wouldn't.
