A short page wins when the visitor arrives with almost no questions. That happens in a few recognisable situations: the traffic is warm, as with your own email list or branded search; the ask is small, as with a free tool, a template, a waitlist, or a trial that needs no card; the product is already understood, so the page is a confirmation rather than an argument; or the decision has effectively been made elsewhere, such as a referral from someone the visitor trusts.
In those cases every extra section costs attention and gives nothing back. The page is the promise, one line of proof, the button, and perhaps a single line that removes the one remaining doubt.
The mistake in the other direction is just as common: a short page for a high-price, high-commitment offer to cold traffic, built because a famous page in another category is short. That page is not clean. It is leaving every objection to the visitor's imagination, and the imagination is not on your side.
The arrangement of those few sections is covered in our guide to landing page structure which walks through what each section has to do and in what order.