some things have slim basis in truth. Crystals do resonate and transmit energy. But believers give them attributes which haven't been proven out. https://en.wikipedia.org/wiki/Crystal_radio

How do entangled electrons communicate over vast distances? If you can answer that question you will be rich and famous for the rest of your life. But the fact that we can't explain it doesn't mean it doesn't happen. I don't believe in sympathetic magic, because ive never seen it performed. But the fact that we don't know how it would work isn't necessarily sufficient argument against it.

Some of your questions there aren't really about how, they are exploring philosophy/morals. If magic were real, yes there would be crimes associated with love potions.

Why don't X do Y - Thats part of why people don't believe. https://www.theguardian.com/us-news/2018/may/12/new-york-psychic-arrested-zoe-fortune-teller

At a fundamental level its faith. And ignorance. But most people are also ignorant of the way their car works beyond the high level basics too.