Until we get some other news, I’ll just assume this is a case where sometimes two people were great together at one point in their lives aren’t at another. This happened to my parents when my sister and I were both out of the house, they realized they weren’t the same two people they were decades before. Thankfully, they’re both very cordial with one another and both happily remarried.
I have doubts this means anything negative for the foundation, other than maybe a rebrand of the name. I live in Seattle and have a few friends who work there - While both Gates are active in the spectacle of the foundation and pushing the broader mission, neither touch day-to-day operations at all.