If a jury can rule against the law, why shouldnt the voters.

Because juries (in some countries, see https://en.m.wikipedia.org/wiki/Juror's_oath ; however, includes France) take an oath to examine the evidence presented and judge impartially to the best of their ability. Voters don’t.

At the presidential level I would say the law should follow the (will of the) people and not the other way around. After all, those irrational voters are the ones who created the law in the first place, in so many ways. As an aside, the more I think about someone being able to truly be impartial, the more I giggle. Myself included, of course.

The main idea here I think is that having someone who’s been embezzling money run for president would greatly undermine democratic institutions and the public’s faith in French institutions. However, the far right will claim it’s a political conspiracy and this will mostly have the same effect.

French politicians have a long history of accusing judges who sentence politicians of being enemies of democracy - the idea being that crooks or not, the people should decide.