hal jordan been the main GL dude since forever. john stewart is cool and shyt, but even fakkit ass guy gardener was more popular than john stewart at one time. Hal been the main GL is damn near all the cartoon movies. john stewarts run on JL was piff, but CACs who actually read DC comics are gonna want Hal. Hal was even a major villain and the reason for one of them retarded ass DC universe resets they seem to do every 5 years
I think the reasoning behind John is aside from diversity, he's more widely known as the green lantern at this point for a group of kids that grew up on JL and JLU. Neal Adams even said that he told DC at the time of the GL movie that it made more sense to go with John and no matter how many comics of green lantern they sell, it pales in comparison to the number of people who watch justice league. Now of course he's a tad bias since John is his creation, but he was right