Making a layered celebration cake for either family or for the cakes I donate is a multi-day process. Much of the steps can (and should be) completed ahead of time.
Most people enjoy the decorating process the most. By getting all the prep stuff out of the way like making the frosting and baking and wrapping your cake layers, you can focus on decorating and packaging the day that the cake is needed.
For me, I purposely split these tasks because I'm a mother of three young children and can't usually complete an hours long project in one go, but also, my brain just works better this way.
Making cake layers and frosting is pretty methodical to me. Decorating however, is more of a creative process and I do best when it's the only thing I'm doing that day. (Between making chicken nuggets and laundry, of course ;) )