[unono]

PG hasn't been running a startup, but managing hundreds of them.

A large company is just a large number of small groups.

A startup is a small group.

PG is someone who has proven effective at managing to give a big ROI from managing quite a few small groups. Hence he is eminently suited to running a large corporation.

[benologist]

YC startups are independent and autonomous, the only people running them are their own CEOs.

[unono]

So PG would be really good at delegating, another plus point for him as future Microsoft CEO.