Not sure if you mean easy to use interface for contributors or for users. I can only judge the second, and the website is "meh"... it's kind of slow and the UI and design is underwhelming.

In any case, being good at what they do definitely helps, but network effects is also a factor. They have the best data coverage, therefore new contributors will mainly chose them over a hypothetical competitor with a slightly better support and user interface.

This discourages new competitors to even try entering the market, which has the usual downsides of a monopoly market such as less innovation.