Igalia is a bit unique as it serves as a single corporate entity for organizing a lot of sponsored work on the Linux kernel and open source projects. You'll notice in their blog posts they have collaborations with a number of other large companies seeking to sponsor very specific development work. For example, Google works with them a lot. I think it really just simplifies a lot of logistics for paying folks to do this kind of work, plus the Igalia employees can get shared efficiency's and savings for things like benefits etc.