Was Hiruzen Sarutobi stupid? Of course he wasn't.
In fact, he was quite politically savvy.
Otherwise, he wouldn't have managed to keep Konoha from falling apart after years of meddling.
The once-powerful Senju Clan had dwindled under his watch.
As for why he let Jiraiya and Minato Namikaze go to the Uchiha Clan, the purpose was simple: he wanted to find a way to rescue Kushina.
To better control Kushina, the Nine-Tails Jinchuriki, Hiruzen Sarutobi strictly controlled who in Konoha could interact with her.
As a result, Kushina had even fewer friends.
Minato Namikaze was one of the friends Hiruzen Sarutobi had deliberately arranged for her.
Hiruzen Sarutobi wanted to use Minato Namikaze to gain complete control over Kushina.
He had begun plotting this plan when Minato Namikaze and Kushina were still very young.
He had even staged a heroic rescue when they were little.
He had the Anbu disguise themselves as Cloud Ninja and kidnap her, then had Minato Namikaze rescue Kushina.
That's right. The battle where the two first met had been completely fake. Hiruzen Sarutobi had arranged the whole thing.
Otherwise, did you really think the Cloud Ninja could infiltrate heavily defended Konoha? Was the Anbu in Konoha just there to eat?
Even if the Cloud Ninja had managed to sneak into Konoha, their strength would have been far beyond what Minato Namikaze, still a student who hadn't graduated, could handle.
That was why Hiruzen Sarutobi believed Minato Namikaze and Kushina had already formed a bond.
With that bond, Minato Namikaze would surely be able to rescue Kushina.
Even if he couldn't, seeing Minato Namikaze would stir the bond between them and make her erupt.
She might even lose control of the Nine-Tails again and destroy the entire Uchiha Clan.
And then there was Jiraiya.
Jiraiya was