It wasn't an easy path to get here, however. The CSS Grid specification was the result of combining three different proposals: Microsoft's Grid Layout spec that had shipped with IE10, Bert Bos's Advanced Layout Module, and Peter Linss's proposal for grid lines. Microsoft's Grid Layout became the starting point because it was already a working tool in a browser. From that start, the draft specification was created by resolving the edge cases that resulted from combining the three models.
Getting to CSS Grid Layout 1.0, however, required implementations before the W3C Working Group was willing to put time into making the specification a reality. Microsoft had an implementation of their own proprietary Grid Layout, but they weren't ready to update it given that it hadn't been widely adopted. That was when Bloomberg stepped in and hired Igalia, an open source consultancy, to write the implementation for Blink and Webkit in 2013. Soon developers were creating layouts with the result. The rest is history as Chrome and Firefox released implementations early this year and finally Microsoft updated their own in October.