When it comes to sentient beings, humans have access to technology and knowledge while animals don't. This means from a long term perspective, assuming moral circle expands of humans expands and technology is used for more good than harm, there are multiplicative benefits of reducing suffering of a human v/s reducing suffering of an animal (who will not go on to build new technology or start a charity).
But making more people care about animals as sentient beings has spillover effects of people generally being able to reason morally about a lot more issues.
#inbox