It IS a division of time and priorities. But I disagree with you on the rest. Owning/running an ice cream stand in LA is different than bringing that ice cream business to GS and running it on team premises. Reportedly, he was not just having pre-game prayers with players. There were SEPARATE buses taking players to each game so those who chose to could attend a pre-game worship service LED by Coach/Reverend Jackson.
Let me put it this way. If you had a boss that said to everyone in your department, "work day starts at 8:00, but I'm also a Reverend and I hold worship service at 7:15 a.m. I invite & encourage all of you to attend so we can get the day off to a great start. We'll meet here, and then transportation will be provided to/from the service." Would you have a problem with that? Do you think employees would feel pressured to attend even if their belief systems are different or they don't believe in religion at all?
So "Separation of Church and State" was not a correct term, but there is still a definite question of ethics in Jackson being the HC and inviting/encouraging employees to attend religious meetings he runs.