If toxic masculinity is self-destructive, and (some) men engage in self-destructive behavior because culture convinces them to, then you still have the question “Why does culture encourage behavior / attitudes that are destructive of everyone (all genders) in the culture?” Is culture self-destructive?

I’m afraid that toxic masculinity creates a culture of toxic masculinity (i.e. a patriarchal culture) in order to justify its own existence. Replacing the toxic masculinity culture (patriarchy) with a healthy culture of equanimity will intensify repressive actions from toxic men — it’s going to be a very difficult fight. But it has to be done, and the sooner we begin, the better.