I think Jacob likes Bella so much because if آپ are a boy and آپ have a friend that's a girl آپ will start to notice that آپ have feelings for her. That's only if آپ two have been دوستوں for a long time.
It's not really something which can be explained. People don't exactly choose to love someone else. Some شائقین theorise that he was drawn to her because she was related to his future imprint though, similarly to how Sam dated Leah before imprinting on her cousin.