Natural progression of any ecosystem. Along with this step is increasingly heavy regulation and confusing BS.
Eventually, many areas will have locked in incumbents which can’t be dislodged using the existing tech and/or tactics. Those incumbents will get increasingly terrible to deal with due to red tape, MBA types squeezing every drop of profit out in a destructive way, internal core value prop folks (engineering, product, etc.) getting more disillusioned or whatever, etc.
Then along comes some change (in market or tech), and the cycle repeats, with much hand waving and gnashing of teeth from some folks (usually older and more establishment) and with much rejoicing from others (usually younger and more up and coming/flexible.).
Next time will YC be disrupting?
Maybe, maybe not.