DDOS attacks are interesting because, as of now, it's basically the only classification of cyberattack that there's no provably correct method to prevent.

Say you get a letter every few weeks from a penpal from years back. You get a few other pieces of mail each day as well, so you quickly sort through them to see if your penpal wrote to you and if so, you pull that message out and throw away the rest.

Imagine you get to your mailbox one day and there are thousands of letters in it. The mail truck comes by for a second run and puts thousands more. Before you've even gotten back to your front door, a third truck comes and does the same.

It's no longer feasible for you to find out if your penpal wrote to you. That's a DDOS.

However, the post office was clearly receiving and processing all of those pieces of mail. They have the capability because they do it every day. Sure, the attacker put some extra load on them, but it wasn't a 100,000% increase like you sustained.

Your mailbox is Github, the post office is Google. Google's infrastructure is set up in a way that there's a lot of it.