It’s related to the density of dark energy, which impacts star formation and the chances of life forming. The idea is that very few universes with intelligent life would have limited dark energy density. While it doesn’t explicitly factor into the Drake equation, dark energy does relate to star formation, which is key to the formula. Hypothetically, a universe with increasing dark energy density is less hospitable to the formation of intelligent life. Likewise, Weinberg posited that very few universes with intelligent life in the multiverse would have limited dark energy density.