What's it really matter?

What's it really matter?
 

-'Grand to-do about this business', he sneered. 'What's it really matter?'

What do the red words mean? The sentence's structure is not the usual thing I know:

-What is it that matters, etc.

What does it really matter?

Even though there's a lot of hype about the business, the person is asking whether it warrants his or her patronage (what is so special about the business that it should warrant any attention).

Excellent answer. But this cannot be explained in the same way:

-Tim asked curiously, 'Who was it saw me?'

I would have said

-Who was it that/who saw me?

But why the original?

"Who was it that/who saw me?" is correct English.

The original can be chalked up to regional usage. It would nevertheless be understood.

Good answer. Thank you.