> Why not buy some companies and get some proper entrepreneurs back into the mix of management?
Because it's inefficient. Google could buy a thousand biotech startups that are all doing innovative work trying to cure cancer and things like that, but that work has nothing to do with search engines or data centers, so it makes no sense to put it under the same roof. The same management staff isn't going to be effective in managing both types of business, all it's going to do is split their focus.
But give the money to the shareholders and the ones who want to can use it to invest in biotech, others can invest in electric cars or new types of power generation or energy storage or space exploration or whatever else.
Using the profits from search engines to fund cancer research and space exploration is great. Running those businesses inside the search engine company is pointless.