There's a matter of debate as to what populism is. And on both ends of that debate are Trump and Sanders.

Sanders is the archetype of an ideological populist, related to socialism, and he believes in governing for the popular good, it is why he is an independent. He's a throwback to early 20th century social programs. It is relatively noble and good. He wants fair redistribution of wealth. He wants to remove wealth's influence from the democratic process. He has a lifetime of track record and governance as proof.

Trump is the archetype of the "thin center" populist. He has no real driving philosophy of governance, and demagogues under the banner of populism. He panders to the religious right even though he can't name a book of the Bible. He panders to the nationalists and bigots. He panders to patriots. And he sets up his opposition, regardless of truth, as the opposite of those things.

Trump is a populist in the way the Goebbels set Hitler up as a populist (https://encyclopedia.ushmm.org/content/en/article/making-a-l..., https://encyclopedia.ushmm.org/content/en/photo/1934-nazi-pa..., and https://museums.nuernberg.de/documentation-center/topics/nat...). That is to say, he is not one at all, he just lies about it to exploit division.

edit: we're just talking past each other. Bernie Sanders is a left wing populist. Ron Paul is a right wing populist. Massie is a right wing populist. My point is that Trump is simply a fake populist. He says populist things and doesn't believe or act on them for the most part. He's simply a kleptocrat with autocratic tendencies.