By that logic, anyone might be the next Hitler; no politician can be trusted.

The lessons of history are manifold indeed, but it has been my observation that when one reads a good book on any period of history one suddenly discovers its immense applicability to the present. WWII is very popular, therefore its histories are popular, therefore we find Hitlers in 2016. In 2020 there will be a new Hitler. In the past, every political opponent was a Nero or Caligula. In the future they will be someone else.

History does repeat itself, but never in a crass or obvious way.