The year after Love Below dropped, so did Kanye's debut. That was probably the biggest influence.
Questlove on Kanye:
Kanye was there and, at the time, he was just, like, Usher's opening act. But watching him control his marching band, I knew instantly that he was going to make noise--
just seeing how passionate his black audience was towards him. Of course, every demographic in every sector of the Roots' graph was anything but inner-city black youth. So seeing that power Kanye had, I thought,
"Wow. This is when we're gonna hand the baton to him, and he's going to be the new leader."
Kanye made the whole "non-gangsta" attire cool for black kids. Common, Pharrell and Dre might have made it cool for him but still.
OutKast & Andre ARE OutKast's. They are the only ones from there movement to really make noise (Cee-Lo blew when the mainstream didn't know of the affilliation). Their success and influence was seen as isolated. Dre had been on that alternative tip since '98 but the change didn't happen till post '04, probably '07.
Kanye dropped multi multi-platinum albums and ended 50's reign. Common dropped 2 gold albums. Lupe's sophomore went Gold.
Andre & Pharrell (Common, Mos Def) too, also influenced the swing. However Kanye is the only one to achieve Rap Mega-Star status e.g. several platinum albums, headlining big tours, introduce new acts, hop on remixes and features etc.