even if the crossbow is easier to load it should still be heavy to pull back the string, if it's easy then there's no power behind it
It's easier because to load a crossbow, because you're using both yours legs, back and body weight to help you pull back the string, not just your arms and back. Once it's loaded, which only takes a second, you can take your sweet time to aim while only exerting enough strength to carry and shoot the crossbow.
Meanwhile, you use only your arms and back for a regular bow and you can't let go at full draw while aiming. While you're aiming, your arms are going to get tired faster than the arms of someone carrying a crossbow, because bow's draw weight > crossbow weight.