Well I think they realized the benefit of open source and how they could use it in their own development. Sort of like Edge is literally Chromium rebranded. You can use chrome extensions in edge and vice versa.  

Only because they have realised that they can make even more loot. They do not have to have so many developers as the open source folk are doing all the heavy lifting,imho. 😎

Eeee by gum a' do laik play on words humour 🤣