Its pretty stupid to judge a coach by how successful he was as a competitor.
This principle applies in other sports as well - bill belichick, phil jackson, tony la russa - average players but awesome coaches.
George farah is the most successful coach around at the moment - he coaches phil heath among others.
His personal best placing was 12th at the Olympia.
Having all the knowledge in the world may not matter as a competitor, but it certainly does for a coach