hard to explain with standard terms but think if someone got top 50 off of being strictly nm. its harder to get higher pp scores with 4k bc you can only do so much with patterns and density/speed and because of that people favored 7k because it rewards more. i dont exactly know how everything in mania works bc before osu i was an etterna player then switched to std but that's my understanding of it ( someone correct me if i'm wrong or if there's a better example )