system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] How could General Grievous lose when he can attack with four lightsabers? It would seem that being able to defend AND attack against ObiWan would make defending impossible.

I don't care how good you are with one lightsaber, fighting against an attacker with four arms that can hold you at bay with two and attack you with two, would be nearly impossible.
gpt
This is how Jedi historian Matthew Stover describes the encounter between Kenobi and Grievous.  

>The electrodrivers powering Grievous's mechanical arms let each of the four attack thrice in a single second; integrated by combat algorithms in the bio-droid's electronic network of peripheral processors, each of the twelve strikes per second came from a different angle with different speed and intensity, an unpredictably broken rhythm of slashes, chops, and stabs of which every single one could take Obi-Wan's life. Not one touched him.  

>After all, he had often walked unscathed through hornet-swarms of blasterfire, defended only by the Force's direction of his blade; countering twelve blows per second was only difficult, not impossible. His blade wove an intricate web of angles and curves, never truly fast but always just fast enough, each motion of his lightsaber subtly interfering with three or four or eight of the general's strikes, the rest sizzling past him, his precise, minimal shifts of weight and stance slipping them by centimeters.  

>Grievous, snarling fury, ramped up the intensity and velocity of his attacks—sixteen per second, eighteen—until finally, at twenty strikes per second, he overloaded Obi-Wan's defense. So Obi-Wan used his defense to attack. A subtle shift in the angle of a single parry brought Obi-Wan's blade in contact not with the blade of the oncoming lightsaber, but with the handgrip. —slice—

So, basically, Obi-Wan's defenses are just that good.