In a fast growing company, all of the people seemed necessary at one point or another. When Indeed was growing, and there were significant numbers job-seekers looking for a place to work who were not using Indeed, then adding features, advertising, expansion of facilities, maintenance, etc. made a lot of sense.

Markets are limited in size though, there are only so many useful features that can be added, new leads to acquire, etc. so eventually, usually when growth slows, a large number of people are being employed without much to do. A classic example of this was twitter, which if you've heard some of the stories from ex-employees required 2-4 hours a week in remote work by their programmers. Mass firings might signal negative financial health in a company, so any executive who suggests it would need to be up against a wall. It's much easier to keep hiring at all costs if you're in charge.

At one point all those employees had something to do, and probably were very productive, but employees have a lot of incentive to "seem" like they have a lot to do, so it might take a while before management realizes 90% of their workforce is working less than half the time.