IT organizations in large companies typically demonstrate tribal behavior in the extreme. This is because IT is a bit weird compared to many other disciplines. The knowledge, in even the deepest most technical areas, is all out there like anywhere else (medicine, aviation, whatever), but the application of it is often unique and/or highly specialized, potentially involving valuable trade secrets and other innuendo with company-wide implications. This leads to a 2-tiered strata in IT, where management and a relatively small number of veteran, senior staffers allow accessions only in carefully, hand-picked circumstances.
So basically what you have is the help desk and everyone else. And it is cutthroat. If you want into one of the biggies (Google, Lockheed, Amazon, whatever) target your company/location and get one of the entry level jobs. Even that will not be easy, as you have already learned. You might need to stalk some people who work there, make friends-of-friends and that sort of thing. Be relentless, get your foot in the door and start career building from there.