I always like to say we aren’t rational, we _rationalize_. Much of our decision making process is subconscious / vibes / “system 2”, but we also have a strong need for a sensible narrative structure to our lives. So what hack did nature come up with? Let us make the gut decision based on a bunch of soft heuristics, then rationalize it and wrap it into a sensible narrative before it reaches our conscious mind. Lets us use our efficient system 2 thinking most of the time while avoiding all that messy cognitive dissonance that would arise from a conscious awareness of how chaotic such a system would be at the scale of… oh, say, a global civilization of such creatures ;)
All rational thought depends on its axioms/premises, and there's no rational way to define a new axiom - by definition they are asserted from scratch, so you need to depend on gut feeling to choose a good axiom over a bad one.
Rationalism "only" works to discard or modify some subset of your axioms when you discover that they lead to incompatible conclusions; which is a good outcome if you want to achieve a consistent theory, of course; but it doesn't help in selecting one consistent theory over a competing one. Again, those preferences are led by emotions.
