Why in anime like JJK and Dragon Ball, sacrificing others make you stronger?

Gojo, Sukuna, Jiren became strong by sacrificing love, relationship, friendship.

I don't think sacrificing these makes you any strong either physically or financially in irl. Maybe it can just save some of your time but if you don't have potential, luck or connections you won't make it.

I would say connections and good relations might actually help you better than striving alone.

Now this doesn't mean friendship and love actually helps. These connections I am talking about are done in a smarter way and not by love or care. Some people can take advantage of other's trust.

Can anyone explain me?

(I personally think potential and motivation are most important while connection and luck plays a role)