My husband thought that no one knew about his drinking, and to a fair degree, he was right. Excess in the world of investment banking was the norm. Remember the 90's? Bankers were the masters of the universe.
Friends and family want to comfort those in the crosshairs of a high-conflict ex, so they offer conventional wisdom. They believe they're offering sound advice because they are reasonable people and it doesn't occur to them that not everyone is capable of being reasonable.