It wasn’t about video length, it was about the Twitter leadership at that time being categorically incapable of monetizing any of their products.
Combine that with the orders-of-magnitude higher cost of running Vine compared to the bird, and it was always either going to be sold off or shut down.
It’s easy to forget that this was back in the time when these companies thought they were changing the planet for the better and drinking their own Kool aid by the gallon.
It’s more about scale. Small open source projects might get one PR a month. Your average tech company is dealing with dozens of PR every single day. Review fatigue is real in these environments