Google stopped needing VC money very fast, by the time I joined in 2006 it had long since been irrelevant. Google was funding the VCs by then, not the other way around.
The DoubleClick acquisition wasn't a merger, and had no impact on anything as far as I could tell. It was really acquired for the market share not the people and iirc every DoubleClick employee was reinterviewed, maybe half didn't make it!
I doubt McKinsey had much to do with it either.
IMO the problem was more that the culture of endless hiring disconnected from need eventually caught up with it. I think once Page finally became CEO he may have decided he didn't like it much, especially as with ever greater numbers of restless/bored employees the flow of negative feedback / hate mail got bigger and bigger. People like Pichai are often appointed as CEOs when founders move on, because they will stick to the founders vision and won't make any big changes. Ballmer and Tim Cook are similar, I think, except that Cook seems to have done a better job of keeping things on the original path than the other two did. Typically under such CEOs revenues and profits increase a lot, but there are few bold initiatives or risks taken. It's easy for drift to set in.
>>One of the things that makes me sad about this is that Sergei and Larry seem so checked out.
I think this one sentence describes everything, companies are all about the people at the top. Its these people that set the culture, pace and overall direction of the company.
If the founders tune out and outsource the very soul of the company to general managers, who can keep lights on rather too well. Well thats what you get. The lights will be on, it will be life as usual and gradual erosion of that very soul that was the company.
You can't blame Larry and Sergei either. There are better things to enjoy when you have billions in the bank and one life to spend it.