Well everybody has had something traumatic in their past. It doesn't explain anything. It's not even the severity of the trauma that's important. I've got a close friend who had the most horiffic and degrading childhood imaginable. He's not into BDSM at all. Sure, he's got issues but nothing serious. I think dwelling on childhood trauma, is mostly just about trying to justify "abnormal" behaviour. If we discard "normalcy" as a concept then it all becomes a whole lot simpler. We just are.
There are other much simpler explanations why some people end up enjoying submissivness, which I find a lot more compelling which are logical.