Unexpected things happen all the time, and sometimes they may be shockingly outrageous at worst, or still a surprise nonetheless at best. When we try to understand others, it makes sense that we would never be able to really get them 100%, as humanity as yet created a way for us to be in someone else's mind.
Understanding is a never-ending process in progress. Another human is as complex as us. We try and fail, then we have to keep on trying, and never give up.