What’s the difference between a blindsided breakup and a breakup?

Been thinking a lot lately what’s the difference between a blindsided and a normal breakup? I get that a mature breakup would consist of communication. For instance if you felt doubt/ uncertainty or had an issue with something and you voiced your issues before it escalated, and tried to let the other person know. Then you guys try to work it out and come up with solutions or if nothing changes/ continues to break boundaries then breakup. But that doesn’t seem to be how it goes most the time, so what’s so different about a blindsided breakup from someone just breaking up with you?