The RethinkDB retrospective[0] contains a lot of insight into how MongoDB has succeeded despite being vastly inferior on a technical level back when it first launched. I have to admit them a certain respect for executing their strategy so successfully.
Choice quote:
Every time MongoDB shipped a new release and people congratulated them on making improvements, I felt pangs of resentment. They’d announce they fixed the BKL, but really they’d get the granularity level down from a database to a collection. They’d add more operations, but instead of a composable interface that fits with the rest of the system, they’d simply bolt on one-off commands. They’d make sharding improvements, but it was obvious they were unwilling or unable to make even rudimentary data consistency guarantees.
But over time I learned to appreciate the wisdom of the crowds. MongoDB turned regular developers into heroes when people needed it, not years after the fact. It made data storage fast, and let people ship products quickly. And over time, MongoDB grew up. One by one, they fixed the issues with the architecture, and now it is an excellent product. It may not be as beautiful as we would have wanted, but it does the job, and it does it well.
[0] http://www.defmacro.org/2017/01/18/why-rethinkdb-failed.html