The military, until very recently, did not do random alcohol tests. Today some units might do them when arriving for work in the morning. While I have no knowledge of these circumstances at all, nor am I speculating at all, it would be entirely possible for a military person to have an alcohol problem, and still complete a full career. The system pretty much encouraged it in years past, drinking was a near-daily evolution (when not forward deployed or at sea), and being hung-over at 0700 was no big thing. The military is trying hard to change that, and has been successful with the newest generation (somewhat, it's still the military, and they're young...)

My uncle flew B-58's, did 30 years, and died in surgery for a liver transplant. I'm over 30 myself, but fortunately for me I'm able to put the glass down and just walk away when it's no longer fun or healthy.