I'm not sure I agree that populism is, by nature, opposed to democracy. I think it is better defined as an opposition to the status quo - which very well may be a democratic government - when that system fails to address the concerns of its people. The voting process in Rome was hilariously tilted against poorer Roman citizens. The only real recourse for anyone fed-up with the senate would be to support a strongman populist who promised radical reform, because the existing voting system (public assemblies) was not effective at representing the will of the people (by design).
I think CGP Grey's video on the keys to power is another great example of this dynamic at play - you only matter when you hold a key to power. Without that, no leader will waste their time listening to you.