You’re oversimplifying things, drastically.

Corporations don’t have one projects, they have dozens, maybe hundreds. And those projects need staffing.

It’s not a chair factory where more people equals faster delivery

And that’s the core of your folly - latency versus throughput. Yes, putting 10 new devs in a project won’t increase speed magically. But 200 developers can get 20 projects done, where 10 devs only finish one.