Yes anybody can cock things up! However we are talking here about a very basic level of airmanship. The AAIB report is fact. Fact is that they believed there was no need for the WX radar to be on. Fact was that they did not see the embedded CBs due to the high level cloud. The fact that they were encountering high level cloud which restricted their outside view should have prompted them to immediately switch the wx radar back on. The premise for them originally switching off the radar had disappeared. This is very basic airmanship.