I think Google's self-competition is something they are doing strategically.

If you look at the industry as a whole products wax and wane based on market trends. Market leading products often struggle to innovate under the weight of their own success and are eventually replaced by a new innovator that's doing something right.

Google, by virtue of creating many different types of products in one category somewhat insulates themselves from this effect. They have effectively infinite money, so from their perspective they can somewhat emulate the greater market internally. They can let "startup" style teams form internally so if someone supplants one of Google's products, it's likely to be a Google team.

There are significant downsides to this (eroding consumer trust) which may take their toll on Google with time.