For me, I kind of think of DID as ego states that got out of control :-) Some people's "primary" or host personality is really strong so they can suppress their knowledge of other ego states, just think of them as odd thoughts or something they occasionally have whereas for some people an ego state takes charge and does really well and the person isn't aware that happened because of trauma so it's likely to happen again and other ego states may try it too, etc. As a child we're less likely to have as much control during stressful times, less likely to have other ways of dealing with really horrific abuse, etc. so more likely to let "someone" who can deal with it do so for us.