Can't imagine charging and seating without first making,inspecting, and chambering a dummy round to verify all is well....which it seems, is the way it didn't happen here.
Not everyone was born with vast knowledge of reloading techniques like you were that allow them to make snotty comments towards people trying to learn. Some people had to learn the hard way by trial and error, often with help of people who had experienced the same problems in the past. It doesn't help the new reloader either that RCBS packages instructions that are fundamentally incorrect with regards to sizing die adjustment with their die sets.