I usually call this a rogue wave in startups, because it isn't really any one factor that does it but in conjunction many factors like the dunbar number, custom

I usually call this a rogue wave in startups, because it isn't really any one factor that does it but in conjunction many factors like the dunbar number, customer growth, overhead, renewals (especially in B2B SaaS), burnout from multiple years of growth all tend to hit right around the same time. It's a very real phenomenon in my experience and I've also used the moment to really gain separation from competitors as well, since the stumbling is predictable at right around this point.