I don't think that is fully the case, 300 hundred devs don't provide in a day what a dev provides in 300 days. Basically the coordination needed between those 300 devs require so much effort that they won't get done as much. I like the comparison with a pregnancy, with 9 women, you can't get one baby in a month. After 9 months you can end with 9 babies or so, but it still takes 9 months.

Having 300 devs is incredibly inefficient, with so many, many of those are just doing menial work. And surely there will be plenty doing less than they would do in a smaller team. The reason for such big teams I feel is double, one, high rotation of employees, like OP, the best ones see the shit show and leave. The worse ones that won't find another job easily remain, unhappy and even less efficient, so the company keeps hiring more. The other reason is, the more employees, the easier it is to get shitty unethical stuff done. Each dev provides a little bit of crap, so little that they might not see the impact or so that they won't feel like fighting it, but combined with everyone, it creates that shitshow.