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collapse of the mainstream parties
It's a hard one isn't it? TBH I don't have a great knowledge of French politics, just a bit of an interest.
One the one hand, yes, of course you can't deny that the mainstream parties have taken a hit and that less trad. parties have gained.
However, France has always had a more diversified party culture than the UK and US. The right rallied around Le Pen and the Centre Right/conservative and Left still did well. And as you rightly point out Macron is not necessarily the outsider some people make him out to be.
So collapse seems a bit strong*. Disillusioned? Looking for alternatives?
Also at the moment I'm heavily influenced by a discussion I heard on the unsuitability of the UK's parties for its current range/split of opinions and demographics. Interestingly in relation to the US, some pointed out that Trump actually just did as well as you'd expect of a GOP candidate - no better.
*or I may be naive and those fig.s equate to a total disruption of the political landscape.
The most noteworthy thing that I've seen reported is the collapse of the mainstream parties (although this is probably slightly over hyped, as Macron comes from Hollande's team, and Fillon did surprisingly well considering the corruption claims).