>>279992573
>don't think Yoshimune was sincere
I think you are reading too much into things and missing the point. Yoshimune's main goal was a stable Japan under a stable Tokugawa rule in the long term. She was certainly willing to humiliate or upset her daughters to hinder the re-emergence of succession disputes. Sure, Munetake would have been a better ruler than Ieshige. Even if she turned out incompetent or spiteful she would be more respected and that is important. But it would set a precedent where every envious 2nd child in future generations feels like they have a claim to the title of Shogun. And think about how this fits in thematically with Hisamichi's confession. Yoshimune herself gained power because her own elder sisters were 'removed' - but did not approve of it.
>she should have acted as a leader but instead chose to be a mother
You have it backwards. Yoshimune WAS acting as a leader, and chose the option which would logically be best for the future of the realm, while ensuring that she (and later Okitsugu) could keep an eye on things in the short term. She knew that Ieshige would suffer as Shogun but told her to suck it up.