Or why they are embedded at EVERY level of the deep state?
Well,
that is more easily answered: it is part of their plan, as it has been for over 100 years.
Another facet of the plan is to lie about it and to demonize anyone who dares point out that Communists have infiltrated our government. Old Joe McCarthy may have been reckless and a boozer, but he wasn't wrong.
But in our military, especially within the academies, there remains a culture and a history that would seem to preclude the acceptance or advancement of anyone with ideas so violently antithetical to those upon which our nation was founded and whose security is at least partly dependent on the success of those military institutions.