I am trying to start utilitising the space under my staircase which is currently enclosed by drywall.

I made an opening through the drywall, and found the diagonal cross bars under the stairs.

First thing I thought that these were critical to keep the stairs in place. Right now I wonder if these are just there to help frame the stairs, and since they are hidden, they were never removed.

I took some pictures from the space which might help, I would like to remove these so I can start using the space under the stairs without the stairs collapsing.

Thanks in advance!

 

Forgot to ask the question

Can I remove these diagonal pieces?

What are my options to use the space and get these removed?

 

That is the oddest framing I have ever seen. I've been in construction all my life and have never seen a set of stairs framed that way. That being said, you should be able to remove the cross braces as their main purpose was as you suggest, to assist in framing. The stairs will not collapse but if you notice there is any movement in them you can put plywood on the wall that runs parelell to the treads in your new closet before drywalling it to add some rigidity.