I also wrote about VS Code's early rising with a focus on marketshare here https://blog.robenkleene.com/2020/09/21/the-era-of-visual-st...
I also think your observation about VS Code's rise forcing JetBrains into a corner is spot on.
On a side tangent, I find it odd that the whole VS Code phenomena is under analyzed. Before VS Code, text editors and IDEs were one of the healthiest software categories around, with the market leader hovering around 35%, which is great for competition enforcing quality (DAWs are still like this today). Now text editors have become more like the Adobe suite, where there's in 800 lb gorilla doing whatever it wants and everyone else is competing over scraps (if you say VS Code is actually good though, Photoshop was amazing when it made its rise too). Developers just let this happen to their core tool without anyone really talking about?