Alphabet and Google is not really a split in the sense people are talking about.
Typically when people say Google should be split up they mean different parts of Google should split. Google has search, ads, Youtube, Gmail, cloud, Android, etc. These parts would be split into different companies. Some parts "go together" like search and ads so they may be allowed to be one company, but YouTube and Search don't go together so they would be separate companies.
But YouTube and ads do go together. Gmail would also presumably have to be Gmail and ads if it wasn't operated for data to feed to the ads engine. I could see Android becoming a product for carriers without ads, cloud doesn't need ads, how would Chrome operate as its own business without ads? Firefox is just paid for by Google search, would Chrome be the same, and would that be different enough to satisfy a breakup? Would you just split the ads team and data among multiple new companies and tell them they arnt allowed to talk to each other anymore?
YouTube could buy ads from a source which isn't Google. It's not immediately obvious that YouTube which uses full video ads is best served by getting ads from a company that focuses on text ads (Google) or banner ads (Google's DoubleClick).
Gmail could charge for account features like Yahoo mail and Fastmail do.
Android could be legitimately open source, like Linux is. Or they could sell carrier specific distributions, which is something carriers are doing themselves right now but badly.
Chrome would need to operate under the aegis of some company, but that needn't be the same company that runs Google search and Google ads. If that were the case, their abusive ad experiences code may actually be good and not merely reflect a desire to destroy ad companies that aren't Google's DoubleClick. Chrome could also then allow browser login integration into other companies. I'd prefer of Chrome integrated with my Apple accounts, not my Google accounts for example.
Ads itself could be split into two companies---Google search ads (which may or may no be owned by Google search), and DoubleClick which was its own company to begin with before Google bought them.
I was just providing an example of the different products vs a geographical split. How things actually are split would be up in the air.
Of course YouTube would need ads. My point was that YouTube doesn't need to be in the same company as search, not that YouTube doesn't need ads. The ad network would likely need to be split into the new companies that are formed so all the parts that need their own ad network could have it.
Chrome likely could not survive on its own unless search paid for it like they do with Firefox. I am not sure all the products/services that Google has and their individual ability to survive without Google. That is something that would need to be determined by the people involved with a breakup.
Typically when people say Google should be split up they mean different parts of Google should split. Google has search, ads, Youtube, Gmail, cloud, Android, etc. These parts would be split into different companies. Some parts "go together" like search and ads so they may be allowed to be one company, but YouTube and Search don't go together so they would be separate companies.