I ran into the same confusion a while back. My local business had a Google Business Profile for reviews, directions, and opening hours, so I assumed that was everything. Later I realized the Knowledge Panel is more about Google's understanding of a business or person as an entity, and it can pull together information from different trusted sources instead of only the business listing. I found this explanation about google knowledge panel pretty helpful because it breaks down how it's different from a Business Profile and why not every business automatically gets one. In my case, keeping business information consistent across the web also seemed to make a difference over time.