I think this is a good case for applying Hanlon's Razor. The person that did the forking and removal of copyright text may simply not know that it needed to stay there.
I would love to know what processes MS is considering to prevent this in the future as well as what kind of auditing might be done to look at other projects that started as forks.
It wouldn't be surprising to me if an expert Leetcoder simply copy/pasted the code, knowing nothing of licensing. What would surprise me though is the engineering team not having at least one open source expert that didn't intervene.
