Both were crimes committed against his family.
Both highlighted contempt & hatred towards the family.
Both were for money.
Julie knew about both of them.
He involved Julie for the caravan break in. After the massacre he rang her straight away. Julie was the first to know about both.
Bamber involving Julie in the caravan break in, made him feel comfortable in discussing massacre plans with her.
Bamber spent some of the proceeds of both crimes on Julie.
Both involved staging a scene.
He would have done reconnisance work before each crime. Aware there was money at the caravan site & aware everyone was at WHF.
Both involved implicating someone else - burglar/Sheila.
Both were crimes that could not be repeated. Bamber would have been disinherited if robbing the caravan site again.
Bamber knew the layout of both locations.
Bamber knew how to enter/exit both locations.
The relatives were suspicious of Bamber for both crimes.
Both crimes effected other family members - AE, RB, AP etc.
If Nevill/June were aware Bamber committed the caravan break in, it would have brought him closer to being disinherited. Motivating him to commit the massacre.
If Nevill/June were aware it was Bamber, he may have been told he has to repay the money. Motivating him to commit the massacre.
Inheritance killers do commit more minor crimes against their families beforehand.
Bamber testified he robbed the caravan site & spent the money out of greed. The same reason he was convicted for the massacre.
The police were not aware he had robbed from the family business. Reducing the risk of being a suspect after the massacre.
The success of the caravan break in gave him confidence to escalate.
The caravan break in gave him instant money & a short term lavish lifestyle. He liked the feeling & wanted it again.
He quickly started spending money after both the caravan break in & massacre.
The massacre was less than 6 months after the caravan breakin. Perhaps at his first opportunity when everyone was at WHF.
The massacre was Bamber's only escalation route to get rich after the caravan break in. He was not a hardened high quality criminal & had no special skills. His only other option was continuing his life at WHF.