He was the Kage when Oro departed. Secondly, if he had killed Oro, there wouldnt be any edo tensei. Meaning no kin and Gin bros therefore no Juubito and Madara. It would have been a bunch of Zetsus and Obito against the entire alliance. They would have been demolished. So yea Hiruzen letting Oro live has caused more harm than good. And don't even get me started on all the countless lives he's killed after he left the village.Ok first off I think it's odd that you're saying he's not powerful enough to be hokage when he was considered the strongest in the village at one point and knew all jutsu.... So basically by your estimations no one should have been hokage.
I'm not saying that not killing Oro made him a better hokage he wasn't even hokage at the time of Oro's departure, all I'm saying is him not killing orochimaru was highly beneficial to the core strength of the current alliance. Orochimaru's life actually helped the shinobi world if you look at the bigger picture because if it wasn't for Orcochimaru bringing back the hokage Obito would have carried out his plan with the 10 tails and no one could have stopped them. Sasuke wouldn't have become as powerful as he is and the Uchiha would have already run over the leaf village. Again I'm not saying that it makes him a better hokage you just can't deny if he would have killed Orochimaru that day everyone would be doomed.
You're saying Hiruzen never could beat Orochimaru? Well Orochimaru clearly respected Hiruzen as someone who could make light work of him even admitting that Hiruzen could kill him but didn't believe he could go through with it... AGAIN Hiruzen wasn't even hokage at the time. Read buddy.
So you're saying Hiruzen would not have been able to seal away the 9 tails even in his prime when he clearly knows sealing techniques as he displayed when he used the reaper death seal on Orochimaru. I'm sure in his prime he would have been able to seal Kurama and you know what if you think about it he's the only shinobi besides harshirama containing Kurama with wood style to be able to physically fight kurama. He swiped kurama away like it was nothing and probably could have sealed it but Minato of course did it himself. It's funny people always want to forget that just about MAJORITY from the leaf that's near kage level including jirya and Oro know sealing techniques.
Please tell me how did Hiruzen fail in everything he did? A line from kiba "DO YOU EVEN KNOW WHAT HOKAGE MEANS!!!?" My guess is you don't because if you constitute bringing the leaf village through an entire generation of prosperity then I guess that's how you see it. But it's really not failure at all. He went through having to cope with the hashest time in the leaf village durring the Uchiha massacares but still remained to keep the village away from war and it's people safe. Tell me what did Hiruzen ever fail at? He succeeded in damn near everything even in death he protected the village from O and a generation of the strongest ninja came up from his reign as leader in office.
He was the Kage when Oro departed. Secondly, if he had killed Oro, there wouldnt be any edo tensei. Meaning no kin and Gin bros therefore no Juubito and Madara. It would have been a bunch of Zetsus and Obito against the entire alliance. They would have been demolished. So yea Hiruzen letting Oro live has caused more harm than good. And don't even get me started on all the countless lives he's killed after he left the village.