> Can someone explain this ideological whiplash?

Yes. The party used to be conservative; now it's populist. They are two very different ideological positions. It changed under Trump. It's the same party in name, but a totally different ideology. Many traditional conservatives have gone along with it because the party still slashed taxes, which has been their main goal for a long time. They care much more about lower taxes than government ownership.

Slashed taxes but raised tariffs (aka import taxes).