Pertinent quote from the results section of the publication:
Most people who come from a socio-economically less favorable background do not commit more crime than people who come from a more favorable background, and it also happens that people from a more favorable background do commit crime. This means that even if there is a connection between socio-economic background and involvement in crime, that connection is weak. It is not possible to appreciably predict who will commit crimes based on knowledge of people's socio-economic background.
https://bra.se/publikationer/arkiv/publikationer/2023-03-01-socioekonomisk-bakgrund-och-brott.html
By that logic, those technologies should have been passed to Africa through Egypt and contact with the Nubians and Ethiopians, who regularly traded both with the African interior and with the Egyptians. No?
Which is why iron tools from the Iron Age were found as far south as Tanzania…