the fewer local shops there will be in the future.

(Grammar Questions I Couldn't Answer)

This one comes from ELT Twitter:
Someone tweets: Weird grammar question from a student I don't know the answer to. Why can't you make this sentence without 'there': The more we buy in big malls, the fewer local shops there will be in the future.

Weird grammar question from a student I don't know the answer to. Why can't you make this sentence without 'there': The more we buy in big malls, the fewer local shops there will be in the future.

— Tim Hampson (@timhampson) June 16, 2021

I respond:

Interesting one. I think the original sentence (before transformation) would be "There will be fewer local shops in the future". This would be the existential "there", as in "there is a tree" But then, "the fewer" gets moved to the front for emphasis

— Joel Swagman (@JoelswagmanJoel) June 16, 2021

By which I meant: "the fewer local shops" all gets moved to the front. 
So I think I got half of it.  But where does "the" come from in "the fewer".  And what kind of transformation is this?