Swinging the censer at Santiago de Compostela, Spain

See 6-2022 updated video here: Swinging the censer (botafumeiro) at the Catholic cathedral of Santiago de Compostela, Spain. It is supposedly the largest censer used in a church. It crosses the nave and into both transepts of this cathedral. This is usually done in the Mass for the Pilgrims and has been done for centuries. The reason why is there are a lot of unwashed masses who congregate inside the cathedral after doing the Camino de Santiago pilgrimage walk. There needed to be a way to cover the odor. Not sure why this is done after Mass and not at the beginning.