Numerous H-53 pilots that I have subsequently interviewed have stated that this helicopter could have been flown on just one hydraulic system, observing certain precautions...."
I take it you have never flown on a CH-53 with hydraulic problems, or know anything about the hydraulic systems of a CH/RH-53D, I was trained by Sikorsky on the AFCS of both which included a complete breakdown of Hydraulic systems and flew as a test crew member on test flights and I will tell you that any pilot that says a CH/RH-53 can be flown with only one hydraulic system functioning has never flown a CH/RH-53D in that condition.
What they undoubtedly said but you didn't understand is that A CH/RH-53D can lose one hydraulic system out of three and still fly, not that one can be flown with only one hydraulic system functioning.
I have experienced an intermittent dual hydraulic failure on a CH-53D Bureau No 157727 and it was the closest I ever came to dying while flying test hops.
That quote is from Colonel Kyle and if you read that post then you know that the Marine pilot of the helicopter felt that it could fly, therefore setting the army part of the operation into action, but his flight leader grounded it and killed the entire mission. If the helo 5 had not turned back then it would have been available if the Navy BIM policy had been known then helo 6 would have been available.
One pilot wanting to fly with his bad hydraulics, another co-pilot trying to force his pilot to continue on to Desert 1.
In the end it was the lack of helicopters that killed the mission.