Civilization isn't the human species, it's a higher level and far more fragile thing. If a small fraction of civilization survived a global disaster in bunkers

Civilization isn't the human species, it's a higher level and far more fragile thing. If a small fraction of civilization survived a global disaster in bunkers, it's very possible they would regress during the aftermath and never achieve a global society like ours again. A self sustaining civilization on Mars guarantees not just our survival in the Darwin sense, but our continued technological advancement and expansion.