If that's the case then why are they ok with the founder leaving? I don't think this is a scam or anything, I just wish I understood the mechanics of how their business works better than I do
By the time the business is "stable, profitable and growing" the founder is likely far less important than in the beginning.
There have to be processes in place to manage the business's day to day operations, and a good management team that looks to the future. You can't maintain a business at that level while still being dependent on a single person so the business at the time of sale has to be capable of continuing on without that person present.