Why did Obi-Wan hand off his lightsaber to Anakin in the fight against Count Dooku?

Question

This has always bothered me. I'm talking about their encounter on Geonosis in Attack of the Clones. The whole scene can be seen here with the saber hand-off in question at 1:36.

After Obi-Wan is injured, he hands off his lightsaber to Anakin who continues to fight Dooku with two sabers at once (until his own gets cut in half a few seconds later).

Sure, it looks cool in the movie and all, but is there a in-universe reasoning for this hand-off? I mean, if Anakin was more effective when fighting with two sabers at once, why wouldn't he do so all the time?

Answer 1

It wasn't necessarily a question of more effectiveness, as of changing the tactics. Up till that point, Anakin was about to lose due to expending more Force energy than Dooku. 2-bladed fight would change Anakin's pattern and thus force Dooku to change his pattern.

Also, it's clear that this wasn't some deep-thought stratagem by Obi-Wan. It was a spur of the moment, desperation-inspired Hail Mary pass.

“Unusual,” Dooku said again. “But not enough to save you this time!” He came on hard, thinking to drive Anakin back and off balance as he had driven Obi-Wan back. But Anakin held his ground stubbornly, his green blade flashing left, right, and down so forcefully and precisely that none of Dooku’s attacks got through.

Off to the side, Obi-Wan understood that it couldn’t hold. Anakin was expending many times the energy of the efficient Dooku, and as soon as he tired …

Obi-Wan knew that he had to do something. He tried to come forward, but winced and fell back, in too much pain. As he collected his thoughts, he reached out with the Force instead, grabbing at his lightsaber and pulling it in to his grasp. “Anakin!” he called, and he tossed the young Padawan the blade. Anakin caught it without ever breaking the flow of his fighting, turning it under and igniting it immediately, putting it into the swirling flow.

Obi-Wan watched in admiration as Anakin worked the two blades in perfect harmony, spinning them over and about with blinding speed and precision.

(R.A. Salvatore's AotC novelization)

Clearly, that didn't quite work as expected, as Dooku adjusted easily and shortly, dis-dual-lightsabered Anakin:

And he watched with similar feelings the working of Count Dooku’s red lightsaber, flashing ahead and back with equal precision, picking off attack after attack and even countering once or twice to interrupt the flow of Anakin’s barrage.

Obi-Wan’s heart leapt in hope as Anakin charged forward suddenly, bringing his green blade over his shoulder and across, down at the Count. Obi-Wan understood immediately, even before he noted Anakin’s blue blade coming up and over the other way—the green blade would push the Count’s lightsaber out of the way, clearing the path for the victorious strike!

But Dooku retracted impossibly fast, and Anakin’s down-cutting green blade hit nothing but air.

Answer 2

Obi-Wan's idea is that Anakin (who has proven himself no match for Dooku in terms of classic lightsaber technique) should do something highly unconventional, fighting with a second blade in the hopes that this somehow evens things up.

But Dooku is right, Obi-Wan thought through the haze of pain and exhaustion. Anakin is no match for him … unless Anakin does something unexpected. Using all his remaining strength, he reached out with the Force. “Anakin!” he called, and flung his lightsaber to his apprentice.

_{^{SW: Attack of the Clones - Junior Novelisation}}

Unfortunately, this turns out to be ineffective. Unbeknownst to Anakin, Dooku has been teaching Grievous who positively revels in multi-blade combat.