It's not supposed to supply 100% of the world's energy needs, it's supposed to be a transitional source to move away from fossil fuels and then to renewables. We can build both renewable and nuclear, or we can build renewable and fossil fuels. One of these is much more harmful for the environment. In an ideal world we could just go 100% renewable immediately, but unfortunately that isn't an option. So it's better to go with the "less harmful" option than the "will literally kill the planet and all of us" option instead.
It's not supposed to supply 100% of the world's energy needs, it's supposed to be a transitional source to move away from fossil fuels and then to renewables. We can build both renewable and nuclear, or we can build renewable and fossil fuels. One of these is much more harmful for the environment. In an ideal world we could just go 100% renewable immediately, but unfortunately that isn't an option. So it's better to go with the "less harmful" option than the "will literally kill the planet and all of us" option instead.