If Yahiko lived, the Akatsuki might continue along its original idealistic path, but in the end, it might still fall prey to cruel reality and the schemes of various factions.
If Yahiko died and Nagato fell into darkness, the Akatsuki would become the terrorist organization that would one day shake the shinobi world. But that would also mean the Rinnegan's power would come fully under Nagato's control-or rather, under the control of Madara behind him-to be exploited.
From the perspective of "milking resources" and "obtaining high-quality material for lies," might a Nagato who had fallen into darkness, fully awakened his power, and become consumed by obsession offer more "advanced" possibilities for manifesting lies?
But...
Images of his recent interactions with Nagato and Yahiko flashed through Uchiha Makoto's mind.
The way Nagato had cautiously begun to let down his guard, Yahiko's naive yet infectious ideals... and that meal of Chinese cuisine that had helped Nagato relax a little.
"Tch, what a pain." Uchiha Makoto clicked his tongue.
He realized that he... rather didn't want to see that red-haired boy endure the gruesome death of his closest friend and the destruction of his ideals, only to plunge completely into darkness again.
Especially since this Nagato seemed to trust him a little more than he had at the same point in the original story.
"Fine. I'll just call it... an investment in a future 'prime cash cow.' A mentally healthy 'Child of Prophecy' has more potential for 'sustainable development' than a vengeance-crazed wreck." Uchiha Makoto found himself an excuse.
He decided to try intervening after all.
Of course, he wasn't stupid enough to jump out and directly confront Hanzō and any forces Danzo might have hidden in the shadows.
His public identity was currently that of a Konoha ninja. The Land of Rain