I am not sure why some are open and some are closed - if I had to speculate, it’s perhaps that the commercial models help fund the team. They come with safety features built-in as well as API-based access (instead of needing to self-host). They word their mission (https://mistral.ai/company/#missions) as follows:

> Our mission is to make frontier AI ubiquitous, and to provide tailor-made AI to all the builders. This requires fierce independence, strong commitment to open, portable and customisable solutions, and an extreme focus on shipping the most advanced technology in limited time.