Those who sneer at populism are unpopular people – Blair, Juncker, Clinton (H) – people who have done well out the the political system and who resent outsiders crashing it.
If the inconvenient plebs vote against the wishes of these unpopular people they brand the vote populist.
Why shouldn’t the Italians vote to come out of the EU snd ditch the euro without being told by Juncker they’re being populist?
Why shouldn’t the Yanks vote for Donald Trump without being branded populists?
Why shouldn’t the Brits vote to dump the EU without being sneered at as chav populists?
Answer: The guys who sneer at populism think they have all the answers.
But, in democracies, the majority of the people supply the answers.
Answers which are popular.