There are other factors at play here, but this is maybe one of the biggest ones. A LOT of these artists are looking at their streaming numbers and the turnout for performances at festivals and assuming they can carry an entire arena tour, often with very mediocre opening acts, at that. There's a lot of work that goes into reaching that level, and besides the obvious (building up an actual catalog of performable songs, working on stage presence and actually putting on a show), a good portion of that work is strategic touring before hitting this stage.
Whoever put this tour together for him needs to not work with him on the next one. No one in their right mind was assuming that Lil Baby was going to do numbers on a headlining tour in Denver or Salt Lake City, especially at the prices they were charging. He's just not ready for some of these locations.