Transform a serie of shapes in one gradient

Hi !

So I have a picture that I vectorize that include gradients in some parts (sky etc.). Due to the vectorisation, those gradients get divided in couple shapes with different colors. I want to merge those shapes into a an only one shape automatically colored with a gradient. I tried the Compound Path tool but it didn't do what I expected.

Example :

I have this serie of shape that comes from a gradient in a picture I vectorized :

Then I used Pathfinder to convert those shape into an only one and then apply manually a gradient onto it to recreate as best as I can the original gradient :

It works fine but it's pretty annoying to loose that musch time and that's why I wanna know if there's a tool to make it quicker (maybe from the vectorization itself ?)

Thank you very much for your help !