"Detoxify"- interesting word. I don't claim to have any special knowledge of the French mindset, but I do think that we are looking at the French elections through a cultural filter.
As I have said on a number of times, I own property in France. My canton (ie several communes as a single electoral district) returned a FN representative to a political body recently. (You must excuse my lack of information - not being resident I don't have a vote, and it took place when I was not in France). Several such members were returned.
In rural areas certainly, the FN is not seen as toxic. In contrast with the UK, where living in the countryside is seen as desirable, the majority of French people living in rural areas in France are elderly and not always particularly well off. The attraction of French country properties to the British (or Dutch or Belgians) is their availability, young French people prefer to live in cities.
Muslims form a rather larger proportion of the population in France than in Britain.The French state is less accommodating of multi-culturalism than is the British state and in some places Maghrebian communities have become ghettoised.
I think that Marine Le Pen has stepped down - temporarily - from the post of party leader simply to give her time on the stump.