It's simple really. They each had contract's with Insomniac. Hero's Tail was not made by Insomniac. Getting the VA's and music right wasn't all that high on their list of priorities I'm sure.

Problem that voids your comment:
Enter the dragonfly was not by insomniac, yet, BOTH of those people returned. Remember?

i assume it's because they wanted something "new and exciting" to add to an already-existing idea. that tends to not work.

it usually works best when you make a whole new idea altogether, or just "draw influence" from other ideas. tweaking things like this tends to just take away appeal from an already good idea, rather than actually improving on it.

This game may of had potential to succeed. Personally, if they would of used spyros model from Spyro 1-4, and the voice of tom kenny and stewart copeland as music composer, im sure this game may of succeeded. Possibly, Legend series may not of happened either.

I think legend happened because spyro was failing after the third game. The highest rated spyro after Spyro 3 and before Legend of attack of the rynocs.

it usually works best when you make a whole new idea altogether, or just "draw influence" from other ideas. tweaking things like this tends to just take away appeal from an already good idea, rather than actually improving on it.

Why in the world were those to replaced? This WAS a main spyro entry, so they should of been there.