He had moderate success and become incredibly rich for someone IN my opinion is of very average ability and he did that by giving the narrative that he was a modern, forward thinking manager and one of the ways he did that was with stats.
Some, me included would say that a lot of people who run football clubs are incredibly stupid and naive and fell for the bullsh1t the big fella spouted.
Allardyce was a very good man manager but tactically clueless, who was quickly sussed out by people who worked for and with him.
The fact that he was given the National job by the FA Suits backs this up.
There are many others who fall into this category, including the one and only Mark Leslie Hughes, who claimed and still does that he assembled the finest and best educated back room staff in world football.