VSCode copied most of the good features of ST and it is free and open source. Just that is enough to overtake it.

I still use it, it is maintained and it is very good and fast, and that it didn't try to reinvent itself is a good thing for me. But it is not a full IDE (not Jetbrains), it didn't jump on the AI bandwagon (not Cursor), and it is not free (not VSCode), so it is not surprising that it lost some market share. But it is not dead.