Why do we live in times of polarised populism?

I contrast these times with the 1990s and 2000s, when I came of age as an adult. We were taught that it was the end of history and that the days of political polarisation had ended. Now we have populist parties and politicians rising throughout the western world. I think the populists fall into two camps; the nationalist right and the radical left. The former is made up of Trump, Le Pen, Liga, UKIP etc and the latter; Sanders, Corbyn, Podemos, and Syriza etc.

Few of these people/groups have achieved political power and those which have yet to produce a radical change in their own image. Though arguably there are second-world examples that have in a few countries (Venezuela, Hungary and Poland). However, this would never have happened in the 1990s and it is a global thing which is not specific to one country or one political culture. I don't think (for example) giving American specific reasons for the rise of Trump can be a full explanation when he has his equivalence elsewhere. Though political culture can be one factor and can certainly define the style of a movement.

Sub-questions:
1) What are the causes? Is this an economic or a cultural thing?
2) Will this die out or is it a canary in the coal mine?
3) Can you predict the political world in twenty years?

I have opinions on all of this and I am sympathetic to the leftist movements. I know this is big stuff and a welcome people to respond from the left, right and centre to give your reasons. I will read any post, no matter how long. :-)