Well in tech there are also higher barriers to entry brought about by the anticompetitive behaviour of the incumbents. Hence startups need to invest more until they are profitable or are killed by the incumbents.

Imagine starting an ad-tech company now and in 2000. Or VR, Wearable, media streaming, hosting etc.

Yes, it seems like a surprising factor to overlook here! Companies are still innovating -- but when they're onto something, big tech takes notice, and it sure seems like they're all but forced to blitz-scale in order to avoid being eaten alive.

Tech is also a pretty wide umbrellla of industries.

A SaaS product is tech. So is a VR headset. One suceeding does not mean the other one will.