I'd offer intra-species conflict. Male bears kill young bears all the time. Not that much, but bear cubs are first protected by being born in the mother's den, then by the mother that can probably physically compete with most males. Take away opportunities for seclusion and tough and strong mothers, then you can make a need for precocious cubs. Alternatively, make the intra-species competition group based. Basically, they "war" a lot. The hard part in having trouble with is making mothers less competitive with males. If pressures encourage the cubs to fight, we should expect that to encourage strong-fighting mothers too. I'm not sure what to offer for this.
But... maybe a handwave is fine. A sexual dimorphism that has petite and attractive females and strong brutish males is a trope people seem to like. "Males come out swinging" adds to that. There's something to be said that this is only an exaggeration of humanity, not a total fantasy. That's probably why people like it.