alt Hacker NewsVP8 was developed by a small company and bought and open sourced by Google on a fairly short timescale because the proprietary codec group had tried to start exerting their control.
So it's not accurate to say that had a lot of companies behind it. That usage came later and even then it was mostly in odd corners of the video industry.
Who originally developed the codec is only half the story. In 2011, 17 companies created a CCL agreement around VP8+WebM. In 2013 Google signed the sub-licensing agreement to keep it free. Any of the legal teams at those 17 companies had the chance to catch it before then. That there were a lot of legal team reviews by the big tech companies involved did not catch everything. The system isn't designed in a way to make that a solid guarantee like it should be.