It converted well MOSTLY because of the audience. I was targeting people who I had a strong reason to believe would definitely be interested.

Another reason was because my ad strategy closely matched my landing page so they had already consumed most of the Landing Page information via the ad, making it quick to sign up.

Lastly I'd say it's because I was giving something and not asking for much. If you go ABOVE and beyond to offer something of value without asking the prospect to do anything for you, it creates a relationship where they instantly feel like they owe you.