Yeah, because Mumen rider could have totally ripped that guys eyes out along with his innards. Saitama got faster and tougher, but he's always been OP. He didn't even need to punch Crab. That's how all non-boss villains have been portrayed in this story. Nothing lasts more than one attack.

He thinks he was a normal guy who got to where he is now with training. That is not the case.

To talk about his tie not breaking is like talking about his gloves never breaking from his own punches. Can't be that strong, right?

One Punch Man has always been one punch man. I daresay he's also one kick man. Or one pull-your-eye-out-with-his-tie man. It's just a cooler way of saying One Attach Man.