This is a common thing but easily explained -

If you are a music page and you add another music page as a target for example - the users and posts being liked are the followers of that page or people that like/comment on that page. Hence it can appear that the likes or follows are unrelated. 

When we like / follow these users - they visit your profile and have a likelihood of liking your page because they've already interacted with a page similar to yours. This is why the likes can appear unrelated but by interacting with those users we get them to notice your page.