> Most out-of-office politicians are on the Biden side; only a few are on the Trump/Sanders side.
At least on the GOP side, it’s because they care only about cheap labor. Free trade to harness cheap labor abroad, and mass immigration to harness cheap labor for what can’t be outsourced.
If by "tear the system down" you mean anti-establishment and anti-elite, I agree. That's an essential component of populism.
I don't think many people would say Biden was anti-establishment. In 2020, Trump hadn't been in office long enough to change the establishment very much.
When Biden ran against Trump, he tried to appeal to voters who were unhappy with Trump, but nobody called him a populist. He was just a normal politician. Trump isn't. Neither is Bernie Sanders.
How do you decide? I can't give you a clear answer there. Still, there is a difference. (Maybe "do they talk like a normal politician"?) Most out-of-office politicians are on the Biden side; only a few are on the Trump/Sanders side.