Synergistic effects, catalytic effects and basic things like van der waals forces. Molecules in energy rich evironments which self assemble and become both antichaotic and self reproducing.

Why does water freeze in star patterns? Why are salt crystals regular shapes? It's energy efficient. They may be local minima in better packing choices but if some number of these arrive at the helical zipper, the rest is history.

Did mitochondria have any idea what they were doing agreeing to be engulfed? Was it a choice in a soup of competing mitochondria, to hide in a fat-bag and acquire skin?

It's a shit answer: it's a posh wordy version of "because".

Feynman said (better) that much physics is "we don't know" built on shakey foundations, that explanation is often invoking primitives we treat as axioms without knowing what makes them axiomatic. All subatomic explanations of particles ultimately go to "we don't know"

Biology is applied physics.