Here's a political scientist's take: It shows that institutionalist explanations don't tell us much about populism. Just as water finds its level, populists find a way to succeed in any political system.
If populists have 10% of the vote, they play a large role in systems with proportional representation. But they remain locked out in majoritarian systems.
But now we know that majoritarian systems may be particularly vulnerable once populists are supported by ~30% of the electorate.
Because at that point, they can either take over establishment parties (Trump, Corbyn) or displace them.
1) Let Boris Johnson take over the party (and the country) on a populist platform.
2) Or be replaced by Nigel Farage's openly populist Brexit Party.
Without much hesitation, the Tories picked 1).
In particular, PR makes the rise of new populist parties more likely. Majoritarianism makes the takeover of existing parties by populists more likely.
[Nearly the End.]
Britain is soooo screwed.
[The end.]