Can't argue with that, even though I find it puzzling you need to refer to it as I would expect voters to vote for their man in the first round. However when they have been knocked out people will not necessarily vote for their favourite hence the margin of popular victory may not be what is seems to be on paper.
In the first round there are loads of options so allegiances are very split. In the second round voters coalesce around their preferred candidate of the final two, albeit someone who might not have been their preferred candidate of eleven in the first round.
This is how it has always worked in the French presidential election. And Macron's 24% in the first round isn't totally out of kilter with first round winners in previous elections, which has been as low as 19% and tends to be lower with a range of broadly credible candidates (in popularity terms) as was the case this year which rather splits the first round vote.