What Factors Influence Brand Presence in ChatGPT Recommendations?

I’ve been researching how ChatGPT decides which brands to mention in product comparisons or suggestion queries. It doesn’t seem to work like traditional SEO. Some brands with minimal content still appear, while others with massive marketing efforts barely show up. I suspect visibility is shaped by broader online signals—like coverage, hiring growth, trending posts, or something else entirely. Does anyone know how to actually measure these factors? Or track competitors to see what boosts their visibility inside AI tools?