It wasn't just Obama as the Clinton purge was a bloodbath. Some of the best military officers at all levels were passed over for promotions.
I watched from here in DC as promotion boards gave promotions to officers with Letters of Reprimands in their file while the best war fighters were given the boot.
I got to watch the mess from the inside, and you are correct, the purge started at the NCO level and went all the way up.