While it's true that TS would have been started with or without Angular, I think OP is largely correct in the influence that Angular's embrace of TS had in TS's long-term success.
It's difficult to see these days, but if you were watching TypeScript's adoption numbers back when Angular made its TypeScript announcement, there is a marked inflection point when that happened. I was running lots of charts and graphs at the time tracking all kinds of data, and in every graph, you could see the Angular announcement in the chart; it's where the line went from kinda slow and linear to kinda fast and exponential. It was a true discontinuity in the second derivative.
We can't run history twice and see what would have happened without Angular, but I think the quantitative impact in this timeline is undeniable.