Mostly intuition combined with the speed of things. I initially looked at Kurzweil's estimates, which has human level AI in 2029, and have been watching progress towards that. When AlphaStar conquered StarCraft, it was about two or three years before I had guessed AI would be able to play a game where you had a lot of disparate information and had to combine it into controlling a lot of different units and situations.

So to me it's still about 2029 or even sooner for human level AI, and I think what I'd consider a Superintelligence would be about 5 years after that. It would work to improve itself but wouldn't be immediately designing new GPUs and things like that, that would take a few years before it had access to infrastructure and resources to get hardware and things made. But I think once a human level ai gets access to all of those things then it can improve itself fairly quickly.