From the Google side I wonder if the underlying logic of these types of acquisitions is actually more originating on the Google M&A department side.

There's probably some infrastructure needed to maintain a corporate Google M&A team which is probably is essential at the size of Google, but I can imagine there is a bit of downtime in between large deals that are actually exponentially value accretive (i.e. Youtube, Nest, etc.).

If the downtime between rational M&A is too long, you probably start having staff attrition, in fighting/restlessness, lack of practice - not to mention a need to justify the existence of the department via OKRs to the rest of the company. Hence the need for some smaller, slightly less rational M&A deals to get done in order to keep the team in a ready state.