To give the other side! Sometimes long pages are information overload, are long due to poor copywriting and a weak offer, indicate a lack of trust, likely have a complex offer / product, don't work well on mobile, are difficult to digest, and are needed due to poor awareness / branding. We can pick a company and say their long or short webpage are what drives conversions - without evidence. https://www.airbnb.com/ has a short page, they could easily go very long as they have no shortage of content. I suggest it is far more important to focus on having a well designed sales page. I.e.; having a strong offer, including the main components on the page, telling a story, engaging with the reader, addressing their questions / concerns / pain points, using emotion and logic in the copy, qualifying the prospect, using micro-commitments before the CTA, using effective visuals and color, split testing, mobile friendly, minimizing friction, etc.