I tink the pop element of Geness really came from Tony. It was more his band than Phil's. I'm sure they were influenced by Phil's love of Motown and soul, but Banks was also a pop music fan and never really regarded Genesis as a prog rock band. I don't think they would have taken a commercial direction if Banks hadn't wanted to. Altough I would agree that by the time of Genesis (Shapes) Phil's solo success was winning the band a new generation of fans.
I agree on several accounts but not on the most important one.
Tony definitely took over after Peter left; with Steve and Phil still being considered junior members and not writing a lot, Mike being more of the collaborative writer, Tony was unchallenged and the most prolific writer. He certainly was a pop fan in his youth, while Peter and Phil had a great love for black music, Mike would lean more towards the Stones and Tony was a self-declared Beatles fan. Even when he wrote songs that might have been considered as pop i.e. Many too Many or Afterglow, although the latter is tricky, his lyrics were not in that purely pop department.
Tony has been often described by his band mates as irremovable, there's no way of making him do, something he doesn't want to to.
That said, there is absolute no indication in his work with the band, that the pop elements were coming from him. He often professed his love for long, proggy compositions, his work with the band backs that up and in fact, if you look at the songs, Mike was first letting some pop elements creep in.
Tony certainly became more collaborative, on Abacab almost every song was written by the band, except three and the key became how Phil reacted against Tony, meaning what vocal lines Phil was able to come up with, on top of the the chords layer Tony provided. Tony has often said he needed the others to edit him and learn to be more concise, left to his own devices he would always tend to wander off or ramble on. So no, I don't think the pop elements were mainly coming from him. Of the three writers in the band only one was a purely pop, R&B-ish writer and he got more visibility.