> Was it everyone agreeing to follow the "main founders" vision, and him being respectful and not ego driven (so that the vision became shared?)

Pretty much exactly that plus providing the seed round. In practice, this also definitely had a lot to do with things working out well to have a center piece that's stable, predictable and a little detached, quite the opposite of a show-off. Buying into a main vision and then transferring it into a vision for tech, marketing, sales, product and operations was much easier that way.

Equity split was 50:others by the way.

Now you might argue this isn't a "real" as in "more equal" cofounder dynamic, but giving away 50% of your company before even starting and then treating those people as equals made a lot of difference, including an enormous buy-in at all key builders of the company. After having experienced how well it played out, I'd do it the same way.