From everything I hear and read.....it has everything to do with being a late born fawn.....and little (if anything) to do with genetics.
I thought that also after everyone on here saying that but I have a friend of mine who raises and sells deer (small hobby farm). This friend of mine bought this BB fawn from another guy 2 years ago. The next year that BB fawn from the previous year grew spikes and my buddy called the guy he bought It from asking him a few questions about this fawn and the fawns dad. The fawn wasn't a late born fawn (like It would matter anyway, pen raised). The fawns dad was also a spike his 1st year and then In It's 2nd year he was a 115" 10 point. This same BB fawn ended up growing damn near an Identical rack this year at 2.5 years old like his dad did. So yes I believe genes are a part of this also.