You're definitely giving them too much credit.  They're merely bowing to public perception.  Every single MP who has just resigned publicly supported Johnson up until that moment.  It's not like they suddenly grew a conscience.  They simply realised Johnson was doing too much damage to their chances at the next election.  They aren't resigning because they disagree with anything Johnson has done.  They're resigning because the court of public opinion won't let Johnson get away with it anymore and these MPs don't want to be seen as being associated with that.  They're just shallow opportunists.  Nothing more.