I'm voting for Biden (or whoever the Democrats nominate) because Trump will cause unnecessary and avoidable human suffering.
The hope for the Earth, and the species that inhabit our planet—including us—is US. Our leaders have failed worldwide consistently and catastrophically. The climate collapse is THEIR doing and they will never stop the destruction.
WE must stop them the way "powerless" people have always stopped evil—through strategic nonviolent noncooperation. That's what ousts dictators and ends empires.
Biden will NOT save the planet, but he will either not shoot, or shoot less at the people who will refuse to cooperate with the Earth's destruction. That said, IF Trump is elected we will defeat him, too. But it will be bloodier. It IS possible that it will be a faster win for us because his brutality may grow the resistance and steel our resolve more quickly. But it may be just as long and certainly the unnecessary toll will be worse.
Anyway, I want Biden in the same way that I preferred Gorbachev to another Stalin in charge while popular dissent ended the Soviet Union. For the same reason.
The movement itself is agnostic on this point. We just want to save the Earth from ruin and establish a humane and sustainable society.