It would go unstable and fly apart

I add video maybe that helps

Can you please explain what is "fly apart"?

At 5:50
Mars comes around it tugs us. Every time Jupiter comes around it tugs on Mars which tugs us, and you have the system that gets impossibly complex for Isaac Newton. At the time he knew enough to say that if you continue this system it would go unstable and fly apart but it hasn't. But he known as his equation works for any pair of objects...