how much did internet usage increase that year, in terms of the number of people and hours spent? what changes happened in the app ecosystem that had google as a default search provider? what other service offerings shut down or degraded that caused people to move to google? how much did chrome browser usage increase over IE and Safari?

there are so many factors to this, its the same issue when target stock drops 10% over a year and people are like "oh it's because they stopped selling plus size bikinis! the crowd has spoken!". you can attribute it to anything but you're basically always wrong if you're not attributing it to at least a dozen different things