Only The Zuck saw the value though. Why didn't MS, Amazon or Google buy insta? Or some Softbank vehicle?

I’m sure the others saw the value too. It just wasn’t worth as much to them as Zuckerberg was prepared to pay. Not surprising given it’s a service that directly competed with FB in the social space.

Probably because Instagram wasn't a direct competitor to any of those other companies (except maybe Google+, which wasn't even a year old at the time that FB bought Instagram). I don't know why softbank didn't get them.