Honestly, I think it's much simpler than that -- the last decade has been a general trend of building more centralized, less resilient systems. The global internet is in an inherently unstable state because of this (i.e. when problems occur, the internet is no longer able to route around them because the problems are internal to large organizations which both control huge portions of the internet and which aren't internally incentivized to separate components -- see e.g. the AWS status images living on S3). These outages are simply more and more frequent as the system's instability increases. And they will continue to become more frequent as time goes on, until organizations realize that they can't control their own uptime unless they run their own infrastructure, at which point the pendulum will start swinging back the other way. Rinse, repeat.
This is a fallacy all humans experience, however, what is the probability specifically that all these problems are unrelated? At what probability is it mathematically impossible that these problems are unrelated?
"Impossible" means "impossible", not "unbelievably improbable".
That's even more true when you ask about "mathematically impossible", as it reinforces the idea of formal logic being the relevant domain, where precise meaning of words is fundamental.
If you adjust your question to be "at what probability is it unreasonable to claim these problems are unrelated?", then the answer is subjective - different people have different standards for reasonability.
I think we'd need mountains more data than we have about the incidents to compute a meaningful probability, anyway.
1) a secret cyber-war is going on...
2) Some entity is installing new spying slurps
3) An (critical) IX that we werent aware of is having major issues... and we dont know who to blame on that one...