A discussion about the benefits and failings of the 6.5 Creedmoor should probably start with it's origins. The 6.5 Creedmoor was borne out of a discussion during down time at Camp Perry between Dennis Demille of Creedmoor sports at that time and Dave Emary of Hornady. Dennis is a high level highpower competitor, former National HP Champion and former National Service Rifle champion. He shared his wish list for a dream cartridge for HIGHPOWER RIFLE COMPETITION. Aside from accuracy and modest recoil, Dennis also listed out availability of factory match ammo and load recipe's listed on the box. At that time, Dennis was shooting a TUBB2000. Not an AR10 or SR25 so this statement is not true;
Ironically the article misses one of the main reasons the 260 and 6.5CM were created for... to fit into a Large Frame AR and the magazines used by them. ( As well as smaller actions then the typical 30/06 size. )
Emary came back with a cartridge that checked all the boxes and was prepared to name it the 6.5 Demille. Dennis and Dennis being the humble guy that he is suggested it be named for his employer; Creedmoor Sports. And the rest is history.
Why did the Creedmoor take off where it's fraternal twins the 260 Rem, 6.5-08 and the 6.5x47L did not? It is a fortunate coincidence that the Creedmoor was introduced as interest in long range shooting was heating up. The Creedmoor's intended purpose, HP Rifle is shot out to 600 yards and out the gates, the Creedmoor was loaded with long high BC bullets. Also true to Dennis' wish list, boxes of Hornady ammo included the load data (though recently I saw that they no longer continue the practice).
Is the 6.5 Creedmoor the end all, be all cartridge? Of course not. No cartridge will ever be. But it did meet the design criteria laid out for it.
Why is it not dominating PRS? well...I don't play that game but I believe PRS can use brakes opening up the stage for bigger boomers with better downrange performance. *(linked PRS article actually says the opposite - PRS likes the smaller cartridges)
Why is it so popular for hunting? I believe that when rifle manufacturers jumped on board, they had to set up the chambering for the longer, high bc bullets the Creedmoor was designed around. Combined with great quality ammo out the gates meant shooters were given a great chance at downrange success. The original design criteria of modest recoil, high degree of accuracy and slick feeding didn't hurt. All this produced a turn-key package that was a great hunting combination out to distances most hunters could ever wish for.