The reason Trump and Brexit succeeded was because there is a massive gap between the governed and the governing. A US friend was an 'anyone but Hillary' voter, as he said that it seemed to him to be a mixture of buggins turn and the continuation of dynastic politics that had been started by the Bushes and looked set to be continued by the Clintons.Trump is at least an outsider, not from within the political bubble in DC.
The same applies in the UK. There are several bubbles - the Islington one; the Westminster one; the inside the M25 one; the Notting Hill one; the BBC one...and none of them seem to have any connection whatsoever with the realities of life for many people. I think many people got sick of being sneered at for not having metropolitan values; and that the capital of their nation seemed like a nation unto itself. No one was listening, and to a certain extent, many politicians/media commentators etc still aren't listening. Debate is closed down frequently; you can't challenge things any more without being called a TERF, or racist and xenophobic, or far right. Again, the threads on here about 'there be dragons' outside London are an example.
You see it on here a lot - so it gets to the point that people won't engage publicly, but will make their views known at the ballot box. When that engagement is shut down by the commentariat, you get a groundswell of quiet opinion that will make itself known eventually, but in ways that can be destructive and costly (Gilets Jaunes anyone?).
It's not just in the US and UK; it's France, Italy, Belgium (massive bubble inside parts of the Ring).
There used to be some measure of trust in politicians, but there is none now. There are some good MPs (mine amongst them), but for the most part they have their bums on their nice padded seats, with their salaries and allowances, and the unedifying spectacle of them trying to work out how to keep their sinecure going without pissing off the electorate, whilst failing to deliver what the electorate voted for, shows what a complete shit shower the current crop are.
I think therefore that Brexit and Trump were a cry for a different type of politics that puts the wishes of the electorate front and centre, that takes note of their concerns with the rapidly changing pace of society, and for people that will tell them the truth, as opposed to spin; and treat them like they have brains.
The above is a bit muddled, but I am trying to do several things at once this morning, and this was my 5 minute sit down in between doing my blue arsed fly impression!