Freshwater runoff from land changed ocean chemistry. Idiots. Where did the freshwater come from ? More than likely increased volcanic activity in shallow waters spewed immense amount of particulates into the atmosphere. Blocking sunlight. Course they have no way of proving that so they ignore it
It’s called snowball earth because it was covered in ice, nice fresh water ice. The melt was from the ice and picked up minerals as it ran into to ocean, changing the chemistry of the ocean.
The CO2 came largely from the volcanos.