Ah yes, the same problem I had in my GPU cooling mod adventure. Was it the paste or the other stuff that did the trick? We’ll never know.
Considering that your card had one of those old blower style coolers, anything is better than that really!
For those of us who want to make their older GPU quiet and don’t have a bunch of fans or AIOs lying around, replacing thermal paste will probably get you 7 °C or more on a 3-4 year old GPU.