^ The problem being that the country will have to live with their mistakes should Corbyn make it and mess things up, so I don't know what the answer to all this is really.
There is no answer. Just as with Trump, if you do have a terrible leader you simply have to ride out the times, point out their flaws and hope the country learns for the future.
You would hope that by the end of Trump's term the US public will have learnt a very important lesson and no one like Trump will get near the white-house again for a very long time. I imagine the political establishment will have learnt some things too, and perhaps in the future they will introduce some stronger laws against election interference and some of the free reign of the presidency which can be heavily abused.
Sometimes people just have to learn from their mistakes, and unfortunately part of that means you have to live with the consequences when they happen.