My understanding was that ice ages are cyclical due to a pattern of variation in Earths orbit around the sun.
I was under the same impression...but I believe, it is also connected to the joining of north and south American changing the ocean flow.....
The ice ages appear in cycles. But this isn’t speculating about why they have a cyclical nature, but rather what caused the first cycle.
Much more convincing as a cause was the discovery that ice age cycles occur when there is a continent at the South Pole.
I used to think that, but the more I learn about boloids, megavolcanoes and the like I can also see other important factors. For example the Long Valley (CA) mega crater just over 700,000 years ago, the Yellowstone megaeruption around 640,000 years ago. Something triggered our most recent major ice age about 125,000 years ago, but the megavolcano Toba sent the temperature even more sharply downward about 74,000 years ago. I haven’t studied time lines on boloid events in the past million years, but bet there would be some interesting possibilities there also.