As an outside observer, it really looked to me like Microsoft had their head in the clouds up until about 2011. It's like the whole decade between 2005-2015 for MS was about recognizing and coming to terms with the multiple "whole worlds out there" and getting past NIH syndrome.
The one place this didn’t apply was your choice of code editor. You could use whatever you wanted and that had long been tradition. I spent a lot of effort getting VIM to work only to realize it didn’t scale well to multi-million LOC code bases.
Really had nothing to do with the size of the file.
An organisation large enough would have middle management and people who promote from within. And they are successful in one culture and it worked even for customers.
Then ...