And now we do have Hetzner replying here (and on reddit), and it sounds like they did indeed communicate the termination well in advance (but for whatever reason the OP didn't notice it at the time).

None of this is to say that Hetzner responded in an ideal manner, and whatever reasons exist for the termination are still not known, but it seems likely at least some of the OP's criticisms of the process are not valid.

Of course now it's too late as many will never come back to review this thread. As often happens on hn when somebody complains about something, the pitchforks come out before there is enough information to really understand the situation fully.