We don't have any evidence other than billions of biological intelligences already exist, and they tend to form lots of organizations with lots of resources. Also, AIs exist alongside other AIs and related technologies. It's similar to the gray goo scenario. But why think it's a real possibility given the world is already full of living things, and if gray goo were created, there would already be lots of nanotech that could be used to contain it.
The world we live in is the result of a gray goo scenario causing a global genocide. (Google Oxygen Holocaust.) So it kinda makes a poor argument that sudden global ecosystem collapses are impossible. That said, everything we have in natural biotech, while advanced, are incremental improvements on the initial chemical replicators that arose in a hydrothermal vent billions of years ago. Evolution has massive path dependence; if there was a better way to build a cell from the ground up, but it required one too many incremental steps that were individually nonviable, evolution would never find it. (Example: 3.7 billion years of evolution, and zero animals with a wheel-and-axle!) So the biosphere we have isn't very strong evidence that there isn't an invasive species of non-DNA-based replicators waiting in our future.
That said, if I was an ASI and I wanted to kill every human, I wouldn't make nanotech, I'd mod a new Covid strain that waits a few months and then synthesizes botox. Humans are not safe in the presence of a sufficiently smart adversary. (As with playing against Magnus Carlsen, you don't know how you lose, but you know that you will.)
As I understand the Wikipedia article, nobody quite knows why it took that long, but one hypothesis is that the oxygen being produced also killed the organisms producing it, causing a balance until evolution caught up. This will presumably not be an issue for AI-produced nanoswarms.