You are technically true. It just happens that Youtube is the dominant video platform and gets pre-loaded in the default seed.

Would they have made the same choice of preloading a default seed if they had no properties in the seed ? who knows

The whole point of Chrome is to push the web ecosystem forward such that Google can build better products on top of it.

This is part of the plan, but I find this angle to give too much credit to Google.

Once they reached a dominant ad network position their whole strategy has been “advancing the web is advancing our revenue”, and it bled into mobile to the point where building and maintaining a whole ecosystem for free makes sense as long as they stay the search and ad engine of choice (that’s the only thing they’ll fight to impose).

Chrome is built in the same optics: push forward the web and webapps as long as search is theirs.

The whole point of Chrome is to push the web ecosystem towards Google such that Google can exert more control over it.

Exactly. They were tired of Microsoft doing it badly and realized they couldn't build on someone else's platform.