Jobs, jobs jobs , jobs, jobs...
With Brexit and with Trump, it seems to me that a sufficient minority of voters were fed up up with being regarded as mere interchangeable parts by big companies who were quite willing to screw them over through outsourcing, dodgy visas and all the other tactics many trans-national companies do to maintain their bottom line. And for many all over the world they have seen their costs of living rise and rise whilst what were good jobs become breadline jobs or the jobs are moved elsewhere, or they find themselves training a PFY from Chennai to do their job.
And they were also fed up that the politicians were always willing to bend the knee to big business but not to their own constituents. The signs have been there if you were willing to listen.
IMHO Brexit and Trump are not the solutions to these issues, but then the right questions have not been asked. And to quote Douglas Adams:
"It is a well-known fact that those people who must want to rule people are, ipso facto, those least suited to do it... anyone who is capable of getting themselves made President should on no account be allowed to do the job."