How much of that is because when terrorists achieve their political goals, we call them revolutionaries, resistance, freedom fighters, and sometimes insurgents. Only unsuccessful terrorists keep that label.

Sometimes, sometimes. Insurrections typically have an obvious oppression they are trying to overcome. Some insurrections have a terrorist arm, but purely terrorist organizations don't have a direct aim other than cause instability. They don't have an end game. So, I think purely terrorist groups tend to not win as terrorists, sometimes they transform in the process to garner more support and subsequently win but not as pure terrorist organizations but will have become more mainstream.

Gwern had a very limited view of "political goals".