Effective altruism, aka. longtermism, is an ideology dreamt up by rich and ultra-privileged dudes to justify them being callous assholes to the rest of the world’s population in the here and now. The basic concept is that the life of a person in the future, who doesn’t exist yet, is of equal worth to the life of an actual person here and with us in the present day. As such, it is excusable – or even virtuous – to make people in the present day suffer (such as by being a billionaire monopolising all the wealth, while billions live in poverty) if, in so doing, you can somehow argue you’re creating a better future for not-yet-existent people. Proponents of this ideology tend to argue that rich people’s lives are worth more than poor people’s lives, because they’re more “innovative” and have more capability to “give”, even if they’re not actually giving.
Longtermism itself is also associated with the idea that the only goal of people in the here and now should be ensuring humanity’s future as a multiplanetary empire (…yup, nerds been watching too much science fiction). As such, they see it as a “waste” to invest money in making people’s lives better, because literally all money should be going to projects that get humans deeper into space and closer to settling other planets (like Mars). It also means that climate change is not actually a problem because humanity’s going to spread out across the stars anyway and escape this “ball of dirt”, amirite. This variant of the ideology is a huge motivator for renowned scumbag, Elon Musk.