Yesterday, I logged into my Coinbase account after a long time and ... It's empty,
I have a small amount BCH and BTC there. 2 transactions were just made and sent all my BCH and BTC to somewhere.
Before that, I did not recieve any email, or 2FA SMS.
Now I lost all and dont know why.
I don't think it was a multy users hack, from what you say, the only victim was you, so, maybe you have a virus in your phone and computer and that way the hackers get access to your login data. It could be a physical hack too, maybe you leave your PC on and some one get access to it, or some one get your access data with a MITM attack at some coffe shop. Try to figure out how it happen to avoid it happens again.