... and gather evidence; it doesn’t happen overnight.

That is the issue right there.

It should not be possible to have a private business that does security/defense work where it would take any more than a simple computer search to find out where their money is coming from/going to.

To get a license to do business with the govt there should be nothing hidden. And that is something people have definitely "call(ed) them up and explain how you know better than they do how to do their jobs"

That is where dark money in politics comes into play. The people that want to keep the private companies private are also buying politicians privately.