Granted, they weren't releasing much open source then, but it was all free to use, and the quality was far above open source alternatives (e.g. think the Visual Studio debugger vs. GDB wrappers).
I think they just naturally figured out that there's zero advantage to keeping developer tools closed source.
https://www.youtube.com/watch?v=Vhh_GeBPOhs
Granted, they weren't releasing much open source then, but it was all free to use, and the quality was far above open source alternatives (e.g. think the Visual Studio debugger vs. GDB wrappers).
I think they just naturally figured out that there's zero advantage to keeping developer tools closed source.