There was a talk at the time, but I can't find the video: http://jaoo.dk/aarhus2007/presentation/Using+LINQ+to+SQL+to+....
Basically, it was a way to cleanly plug SQL queries into C# code.
It used this sort of ordering (where the constraints come after the thing being constrained); it needed to do so for IntelliSense to work.
And FROM-first syntax absolutely makes more sense, regardless of autocomplete. You should put the "what I need to select" after the "what I'm selecting from", in general.