Every time this is asked I have a different answer. Do you know why? Because there's a lot of things that do this and it's all dependent on the timing and a lot of other factors. The reality is this:
It has nothing to do with her. Nothing. Jack-sh*t. What makes a man fall head-over-heels for a woman is his state of mind, his openness, his willingness, the stage in his life. It's the same with women really; young girls go for things they would NEVER go for when they get older and vice versa and the reason is because you as a person change with time so what your needs are today will change too.
Other than that it's generic nonsense like "kindness, intellect ... " yatta yatta which are A ) ambiguous; what one person sees as intellectual is almost always beneath MY radar and above others' radar so there's that and B ) common: most people aren't going to be mean to you. It's just reality; they aren't! So wanting a "kind boyfriend or girlfriend" is kind of like looking at the 90% of the population and going "I want ... one!" Go ahead.
So then those traits are outright lies and we're wired with more and more intricacies that are subconscious or even primal and instinctual.