You are interrupting someone. That means you need to give them a reason to keep watching within two seconds.
On YouTube, people choose to watch. In a feed they do not: there, you interrupt. The first few seconds decide everything, the picture is vertical, and the sound is usually off. Those are not details; they are the starting point.
Which opening lands cannot be predicted in advance. So we make several variants per topic and let the numbers decide. Whatever works, we scale up through Meta or TikTok.
Turning a landscape corporate film into a vertical one gives you a video in which everyone is half out of frame. Vertical material has to be shot vertically, or at least framed wide enough to allow that crop.
A question or project on this topic?