The Cub Scout program is made up of K - 3rd grade "Lion - Bear" Dens where the Adults run the program. The Adults organize and run the program/dens prompting the kids on what to do.
Webelos on the other hand is for 4th and 5th grade children. Webelos is a two year program designed to prepare older Scouts to join a Scouts BSA troop while learning outdoors skills and participating in many adventures with the Cub Scouts. A well-run group of Webelos is a gradual change from being an 'adult-run' den to being a 'scout-run' patrol ready to fit right into an adventurous Scouts BSA troop. This migration requires the parents and den leaders to give the scouts more and more control, decision-making power, and responsibility as they progress in skills, abilities, and maturity.
The Webelos program has two major milestones - the Webelos rank badge to be earned toward the end of 4th grade and the Arrow of Light to be earned in 5th grade. The final part of Webelos is bridging over into a Scouts BSA troop selected individually by the scout. Once the goals of Webelos are understood, the methods of the program make a lot of sense!