Before I attained my PhD I wrongfully believed that most intelligent, hence highly educated, people I had met who lacked common sense to the enth degree did so because they had so much information to cope with that other matters slipped by them to the point of even causing them to be  insensitive! Insensitivity to the extent that they hurt people’s feelings without knowing it and lacking in simple protocol. Also lacking in common sense such as what to do if the catered food doesn’t show up for an event when everyone has turned up and leaving everyone hungry.
Well intelligence has nothing to do with it because it takes i. life skills, ii. learning to care about the impact you have on others, iii. being alert to what solutions you can activate even if others are negative, iii. becoming proactive using your intelligence instead of sitting on it!