And remember Quibi [1]? Short-form video in vertical format specifically for mobile devices? They didn't have every aspect nailed, but they were definitely trailblazers on that front.
Quibi launched in April 2020. TikTok by this point would have 2 billion downloads [1]. It's difficult to assess they were trailblazers here. I might even say a component of their failure is free mobile video was widely accessible by this point.
Didn't have every aspect nailed? Definitely trailblazers? Quibi is a prime example of an absolute business wipeout. They got a bunch of investor money together, showed no interest in what viewers actually want, and then went down in flames immediately upon public release of the product. The whole thing was a disaster that didn't accomplish anything beyond putting a bunch of capital in the pockets of C grade C suite players.
[1] https://en.wikipedia.org/wiki/Quibi