Gamelin was old and stuck in his ways, petain actively threw his lot in with the nazis and ushered in some of the persecution they are infamous for in France.
I suppose war, like business is quite easy, back the bigger belligerent and you'll often come out on the winning side. Ethics and morals and all that stuff don't tend to mean an awful lot when they're written in the books that go on the fire first.
There's no way I am going to defend Pétain, far from it, but I think this point is something that is often not focused on enough when discussing conflict et al.
As I've said before, hindsight is wonderful thing for us to use, but the real issue is you never have it at the time. We need to put ourselves into their shoes!
As Cicero said, "Inter arma enim silent leges," which roughly translated as '
In war, the law falls silent.' It's easier to be a saint when not in such dire circumstances.
Pétain's desire to retain some form of French control over its own land home and abroad, rather than a full German takeover, is somewhat understandable.
But, I think we can all agree the lengths he went, and perhaps other motives for his actions, went far and beyond that.