It is interesting to think about. Someone like the first manager is actually very valuable at a company where people leave very quickly, especially in an industry where most of your coworkers will have been at the company for less than 5 years.

How much can you truly know about the system if you're going to leave the job in a year or two? How much would you invest?

The only issue with the first manager, IMO, is that they weren't willing to share knowledge or help elevate others. You can understand as much as them and still encourage others and help people grow.

No reason why the first manager and second manager couldn't be a single person.

But what if the first manager leaves? He's made himself too important.

Someone might think so, but ultimately, nobody is (too important).

I think you're reading things into it I never stated. Like, those meetings weren't "haggling minutiae with stakeholders", he wasn't a good buffer. I couldn't "build" when I didn't know what to build.