Rimuru got reincarnated as a incubus who got a power to give and take Magic from people he fucks to heal and empower them, he uses this to heal the goblins, and for fun.
The Direwolves only had the alpha for a male because he didn't want any competition for being alpha so he killed all males when they were born and while they attacked the goblins they only killed the males because they were the more powerful fighters and were going to use the females for sex by the Alpha Direwolves.
