I believe it became popular due to the following: It had a flexible data model as there is no predefined schema. The selling point was rapid protoyping. The J

I believe it became popular due to the following: It had a flexible data model as there is no predefined schema. The selling point was rapid protoyping. The JSON-based documents meant developers could work in objects without an ORM. If I remember Mongo called this "fixing the data impedence mismatch." Sigh. It had decent performance as long as your working set fit in RAM as it was basically a mmap()'d file. It was easy to get up and running. It was in the right place at the right time during the original NOSQL hype cycle.