Depending on what a developer calls content. Some of it can be created with fairly small teams. Over the lifespan of a product, you actually need smaller and smaller teams to develop the same volume of content.
Development pipeline and team autonomy improve over time usually. Things like writing and design eventually need like a handful of people over time. This is why you may often see once larger development teams eventually broken down into other projects while still putting out expansions, updates, DLC, etc for existing products. Very often this is when new development starts too. Turbine were masters of this- they would get crazy development turnaround between projects because they had some good team managers.
Modeling and art assets can be reused and most of the time the animation rigging is canned. It's not common to keep a huge art and animation staff on hand long term. Only a few very large and very rich companies do that- and is arguably a waste most of the time from a development POV. But it looks bad publically to say you're laying off staff or combining project teams; even if it's 100% necessary because Phil and Jane have nothing to do 8 hours a day.
VO and sound are the most expensive things. Most of which has to be outsourced and there is an implicit cost you can't really negotiate. Acting and a lot of sound work are controlled by guilds. Actors, audio engineering, etc. Even recording studios are an additional cost and that still leaves out hiring a director. Which you have to do most of the time and even have to agree to work with certain people- again, guilds/unions. A lot of VO and sound work is reused from past recording sessions- you are paying for the studio for a whole day, you don't stop recording ever until they kick you out basically.
Around 2017, I was working with WB Games San Francisco for a bit which led to doing work for WB Games Albany. They could have like 8 people developing content for their mobile games which receive twice a month updates. New characters, events, stories, etc. I think the total staff working on 3 concurrent games across two platforms was around 17 or so, with most of that Troy staff being administrative (such as myself).
It's like a hospital really. There are relatively few doctors, the docs are super important, but you don't need as many doctors as support staff. And the more efficient the hospital, the less you need of all staff. You don't necessarily need a person each to change bedsheets, another to fluff pillows, one to draw blood, and a fourth to sweep. You have specialists and general staff. The general staff is always gonna be there but is more transitory. And there is a lot more general staff than doctors.