Final answer:
Semir Osmanagić is the primary figure advocating for the existence of Bosnian pyramids, although this claim lacks support from the scientific community.
Step-by-step explanation:
The major proponent and investigator of the Bosnian pyramids is Semir Osmanagić. He has been the principal figure in promoting and researching the hills in the Visoko region of Bosnia and Herzegovina as ancient pyramids, a claim met with significant skepticism within the scientific community. While there is a fascination around the topic, the scientific consensus regards the so-called Bosnian pyramids as a natural geological formation and not man-made structures.