It also frees the management from "fear of God", which results in ridiculous investments and initiatives, accelerated (and unnecessary) hiring, proliferation of middle management, empire building, politics, etc, etc.
It doesn't really matter if the "God" is Wall Street or a holding company like Alphabet.
Only that I'd trust a holding company to be forced to maintain the company in order to not risk its value. A stock holder on Wall St just wants as much profit as possible as fast as possible, and if it goes bust then you can always sell shorts and still profit.
On the other side, Google doesn't always follow this rule and I wouldn't trust them much more to look after Twitter than Wall St.
Google has killed off (or left to rot, and then kill off) projects with huge user counts/business outlooks in the past... remember Google Reader and Google Code?
Both could have kicked Feedly's and Github's/SF's asses multiple times over with a bit of investment, and Google basically let them rot until the backend of Google's infrastructure changed too much to justify the needed adaptions on the projects.
I believe G+ had 300M+ users at the time, and G+ was still considered a failure. 1M is a rounding error by Google standards. They can get 1M users by releasing _anything_ that does _anything_ at this point.
It doesn't really matter if the "God" is Wall Street or a holding company like Alphabet.
Only that I'd trust a holding company to be forced to maintain the company in order to not risk its value. A stock holder on Wall St just wants as much profit as possible as fast as possible, and if it goes bust then you can always sell shorts and still profit.