So Zeus has daddy issues. Not like how most people have daddy issues. Cronus wants to literally eat Zeus to prevent his wife Rhea from spending any time with the kids. He might also be worried one of them might supplant him as king of the gods.
Cronus has already done this with all of the other kids, but Rhea pulled a switcheroo when it came to Zeus. She wrapped a rock in a blanket. Cronus fell for it.
I’d like to take a moment to point out that titans are not the brightest of beings. I mean, I’m not expecting godly intelligence, but being able to tell a living being from a hunk of granite is a basic requirement. Cronus failed.
He swallows the rock whole, just as he’s done with every single kid before. Zeus, meanwhile, is raised by wild animals and taught how to be cunning. He grows up and realizes that he is not actually strong enough to take on dear old dad single-handed. So he does the smart thing. He frees the other titans, specifically the hundred handed-ones and the Cyclopes—who forge his thunderbolts. (These are different Cyclopes than those that Odysseus encounters much, much later.)
With his allies, Zeus easily defeats his father. The myths vary, one says he actually cuts Cronus open to release his siblings. Another one says he just makes him vomit them all up. Either way, it’s a family reunion and Zeus takes over as king of the gods, either decapitating dad or imprisoning him.
This is the second time where we’ve seen the son replace the father, which makes for a disturbing trend, really. It would be one thing if the father passes away or willingly steps down from the throne, but both with Uranus and Cronus we see violent overthrow of the king.
Granted, it’s not undeserved. Both Cronus and Uranus were total jerks (feel free to replace that with a stronger word). It’s an odd precedent to set with the first two rulers, though. It seems to be a model for Greek politics that if one ruler is sufficiently corrupt or tyrannical, it’s okay to overthrow him.
I’d also like to point out the role of the wives in this, too. In both cases, they were the impetus for the sons to overthrow dad. It’s a shame that Cronus followed in Uranus’s footsteps. We’ll have to see how Zeus does.