Le pen got far more youth votes than any other nationalist candidate.
When the left looses the youth, there done.
Funny thing is the left is spinning this as a victory while failing to mention the ridiculous growth of the NF's support base. Just to give everyone an idea, in 2008 they had a 4.5% support. France has a dual vote election system, the first vote is a huge list of different parties candidates and the top two go on to the national election.
So
2007 (presidency) 10.4%
2008 (cantonal) 4.5%
2011 (cantonal) 15%
2012 (presidency) 17.9% (third place)
2017 (presidency) 21.3% (first round) / (33.9% second round)
This is basically a minority party who's support is growing at an astonishing rate. The big left wing parties were defeated in the first round and left a moderate-left traditional party and the super nationalistic right party. So the real story isn't in Macron's victory, which was easily predicted but in the fast growing support of the nationalistic party.