According to the lecture, what is the key success factor for social media video?

Captions are the key success factor for social media video because a significant portion of social media users watch videos with the sound off. Captions ensure your message is still conveyed and understood, regardless of whether the viewer has audio enabled. Without captions, much of your content's impact and reach would be lost. Calls to action are important for conversion but don't address the fundamental issue of initial comprehension. Lighting is crucial for visual quality but doesn't solve the sound-off problem. While video length can influence engagement, it's secondary to ensuring the content is accessible and understandable in the first place.