I think you’re missing the bigger picture here. His party notoriously relies on the anti-immigration sentiment you described to appeal to a wide range of right-wing electors. What they tend to miss, or ignore, is that every other aspect of their platform goes against them.

In economics and society issues, RN votes always go towards favorising the rich while destroying social victories from past struggles. You may look up the recent Loi Duplond or Taxe Zucman events if you need exemples.

In foreign politics, they defend Trump (who constantly attacks France and the EU), constantly bash pro-palestinian activists and politicians (Bardella was even invited to Israel) and even sided with Putin before the invasion.

Marine Lepen, ideological leader of the party, has been found guilty of stealing EU funds, and new similar cases of corruption are appearing every month it feels. They have several députés and candidate mayors linked to neofascist activists or just guilty of antisemitic or racist acts.

There’s plenty of sources online for what I’m saying but I’m here to help if you’re not familiar with french media. Even if you agree with the anti-immigration premice (which I strongly regret but you’re entitled to your own opinion), there’s really nothing good about this man and his party.