for whom

As for the industrial workers for whom the free land was supposed to provide a “safety valve,” they had neither the skills nor the inclination to become farmers.
What is the purpose of “for whom” in the sentence above?
Can I omit it without changing the meaning of the sentence?

It’s more elegant (and the grammatically correct traditional means of saying) than:

Regarding the industrial workers that/who the free land was supposed to provide a ‘safety valve’ for, they had…

You cannot omit it without adding the preposition ‘for’ before the comma.

Good morning, Beeesneees!
Thanks for the help!
I got it and I want to ask you one more question. To be sure, is there any rule say that after “for” we have to use “whom” not “who”? I think it is correct but I don’t know if there is a rule like that.

Generally ‘whom’ is the correct form but in modern English ‘who’ is often used instead. Traditionally it would usually be considered incorrect.