The gilets jaunes protests were touched off by Emanuel Marcon’s new carbon tax on fuel. These taxes were structured to fall hardest on the lower and middle classes, and they came in the context of taxes on the wealthiest having been recently cut.
Marcon is not a leftist; he styles himself as a centrist and a self-professed “economic realist,” in the typical centrist’s sense of “reality:” the duty of those on the bottom to realize that they deserve to be on the bottom, and deserve to get the short end of the stick while those on the top of society deserve more privileges (and any questioning of this sort of arrangement constitutes questioning “reality”).
It is worth pointing out that carbon fees and taxes have been enacted in other jurisdictions, where they generally have not proven so controversial. This makes it fairly obvious that the problems in France are happening because of how the French government chose to do things, and not because of anything intrinsic to charging for carbon pollution itself.