Sorry to hear OP, that you were scammed this way.

Twitter is flooded with these scam comments these days, and it's good practice to never send random people money that you see on twitter anyways. Telegram has had its fair share of impersonators, with multiple scam ICOs posing as Telegram's official ICO and scamming investors this way.

As SFR10 said, the scammer used a fake twitter account to do this. He didn't actually take over the real Pavel Durov's twitter account. It's a common tactic for scammers on twitter to comment on popular exchanges, crypto public figures, and crypto wallet's tweets and promise to grow your funds x times. They are invariably all scam.

Seems like you were the only person to send any BTC to the BTC site, and there was one person that sent 1 ETH to the ETH version. Hopefully nobody else falls for this, and good luck in recovering your funds, though it's unlikely since a variety of fake identities are probably used.