This is a little misleading. The data they quote is based on their previous article[1], which just uses this analysis[2] provided by a VC company. Funnily enough the same VC company put a seperate clickbaitish article just a year before that one, claiming the exact opposite findings (about startups ditching SV).
I would guess a lot of these annual trends are just random fluctuations in their dataset, though to be honest I wonder how they're even trying to estimate this kind of information.