Populism is a reactionary movement. It doesn’t just spring up out of nowhere - it comes to be specifically if and when there’s a relatively common perception among the people that the government no longer serves their interests.
The solution then is simple and straightforward, at least in principle - all it takes is for the government to institute the necessary reforms to win back the trust and support of the people.
The problem comes because all too many politicians don’t have the necessary empathy, integrity and/or determination to actually do that.