Karate is name for tradition.

Karate is arts, not sports originally.
Yes, actually, Karate became sport too, but Karate as sport is not all part of Karate.

Arts don't have rule, but sports have.

This martial arts Karate didn't have certain rule 100 years ago.

Even today, we can see various types of different rules and competition. Therefore, Karate, the name is one, but it is not one title of sport activity.

Some schools are doing WKF style non-contact Karate, but some follow different rule of competition, like hard contact combat competition.

But they all are Karate.

So, what is Karate?

The name is for tradition.

Karate was created in Okinawa, by many people. The island has very good access to the rest part of Japan, to China, to Taiwan, and to South East Asia. Many people brought martial arts and body training method into Okinawa islands.

Okinawan people mixed those arts and formed Karate.

Because of this birth history, even in Karate, there are many different techniques. You can find each master's skills are a little different from others. (Actually, this is very natural. Because human bodies and tempers are not same between humans. So, skills should be changed. Big guy and short man can't use same technique.)
But the different arts are bound by the name of Karate, because they are origin place is Okinawa of Japan.

If one martial art has root in Okinawa, the art can use title of Karate.
But it has nothing to do with Okinawa, it can't be Karate.

For example, some masters are specializing techniques for MMA fighting. The techniques became different one from old Karate. But we can still recognize the new skill as Karate.

Contrarily, if someone made very similar martial arts to Karate today, somewhere in the world, he wouldn't use name of Karate, and we also don't think "he made Karate".

Therefore, the name of Karate is for tradition, not for rule and techniques.