You don't understand anything about either term you used.

Populism is not and has never been a right wing thing. Populism is the idea the the people should control society and their interests are more important than abstract concepts like the economy which benefit primarily the elite. The term has no political leaning.

Rent control is not a leftist policy. It's neoliberalism. Neoliberalism is not leftist in the slightest. It's simply a rebranding of right wing policy.

Rent control is populism.

Rent control is not a neoliberal policy - neoliberalism promotes free markets and de-regulation with which rent control does not align to.

populism: "a political approach that strives to appeal to ordinary people who feel that their concerns are disregarded by established elite groups."

ordinary people = renters

elite groups = rentier class

democracy = mob rule

When more than 50% of the populace are renters they have the power to enact rent control in democracies.