While I agree if Marine Le Pen had been voted in it would have been a disaster, things are not as simple as you say. Just like things weren't so simple with Trump in the US.

Marine Le Pen actually got the majority of the vote in the different Outremer provinces of France, which are mostly peopled by blacks and Indians. You can see the welcome she got when she for example visited Guadeloupe. If you click on the article you will see that the only white face in that picture is Le Pen's:

https://www.lesechos.fr/elections/presidentielle/presidentielle-loutre-mer-bascule-en-faveur-de-marine-le-pen-1402637

And Le Pen is also popular among certain sections of immigrants, including Muslims.

https://www.france24.com/fr/20120427-election-presidentielle-marine-le-pen-front-national-fn-vote-etrangers-immigration-temoignages