I am totally spitballing and speculating here, and everything MOO, but after digging around TB's social media (FB, Twitter, LinkedIn), and looking at the church college/franchise where he got a degree and started his own franchise...
I'm getting sort of a DeAngelo/GSK vibe from TB. "Normal" enough that he was getting away with stuff, but if you scratch the surface, he's boiling over with rage and resentment. This sense of misunderstood superiority and grandiosity... a perception that others are having successes and happiness in life that they "don't deserve" (but that GSK/TB do deserve and aren't getting). GSK and TB being underachievers compared to what other men in their social status, age group, and military record typically achieve, filling them with resentment and rage directed at everyone but themselves, especially women and girls. I think the idea of punishment, and being the one with the authority to dole it out, is very central to TB's crimes (as it was to GSK) and his focus on women and possibly Catholics. If I were the authorities, I'd be looking very carefully into any crimes that occurred in the Jewish community where he worked as well. I see his motivators as being resentment/religion/sex.