You're talking about a team that had the likes of Ronaldinho, Messi, Henry, Eto'o, Xavi, Iniesta, Yaya Toure etc.
I think it's pretty fair to consider that as a factor when talking about Guardiola's success with them. It's not like he took 4th place scraping squad full of Denilsons, Bendtners and Djourous and coached them into treble-winners in a season.