I think most people have it wrong.
Des was not a fraud, or a bad coach.
The answer, at least to me, is clear and simple.
Des WAS a good coach, he fortified a siege mentality amongst Manly and got them to play for each other. He engineered some clever tactical backroom analysis tactics not seen before.
When he came to the dogs, he had great success with the ball playing steamrolling forwards. It was effective and somewhat original. He also lobbied successfully to get the most advanced technical facilities in the league.
The problem was, he was a two trick pony.
He couldn’t reinvent himself when teams figured him out. He was out of ideas. He could change once, but couldn’t again. He also didn’t have a great eye for talent, but that’s ok as you should rely on your recruitment staff for that.
Sport is littered with these examples of shelf life expiration. Success in sport is often categorised or defined by catching the opposition off guard and by complete surprise, before the rest of the pack catches up, studies it, and counters.
Logically, you can’t expect someone with a good idea to keep coming up with fresh groundbreaking ideas again and again.
Same way you couldn’t turn a prop into a centre and then into a fullback.
In summary,
A good coach. Just figured out by opposition. Ran out of ideas Circa 2015.