Content is king! A much worn phrase that is repeated ad nauseam in all courses, manuals and marketing blogs. Very worn but effective, after all. Without content, there is no way to show that you really know what you are talking about and earn, as well as the confidence of your reader. Especially if you want to sell.
When designing your sales page, when you are ready to launch a new product, you have it clear. You have already read a lot about the subject. You have to convey an emotion, connect with your potential client and get them to fall in love with your value proposition. And all this in just two minutes.