>Why did all of them not stop this headcount increase if it's as easily reduced as "too much headcount bad, smaller headcount good"?
For the same reason that colleges and universities have seen their administrative bloat skyrocket at 10x the rate of student enrollment. Administrative bloat inevitably creeps into all large organizations. Many of the people in the trenches making hiring decisions weren't considering the overall financial performance of Twitter as a company. They were making hiring decisions based on what was happening in their own department, or how that decision would help advance their own agenda, or increase their budget, or increase manpower on a favored project. When you further consider that many at Twitter openly conceded (and in many cases, bragged about) that they viewed their role at Twitter as moral arbiters of society, crucial to policing the discourse of the public, it is not hard to see how enlisting as many true believers as possible to the cause would be seen as desirable, regardless of the larger financial implications.
For the same reason that colleges and universities have seen their administrative bloat skyrocket at 10x the rate of student enrollment. Administrative bloat inevitably creeps into all large organizations. Many of the people in the trenches making hiring decisions weren't considering the overall financial performance of Twitter as a company. They were making hiring decisions based on what was happening in their own department, or how that decision would help advance their own agenda, or increase their budget, or increase manpower on a favored project. When you further consider that many at Twitter openly conceded (and in many cases, bragged about) that they viewed their role at Twitter as moral arbiters of society, crucial to policing the discourse of the public, it is not hard to see how enlisting as many true believers as possible to the cause would be seen as desirable, regardless of the larger financial implications.