Just saw this, thank you! I'm honoured to be listed alongside these insightful forecasters — and thank you for running it. I found this competition very fun and motivational, and think this kind of thing works well for fixing some incentive problems.
I can't say why more people didn't submit, but I can say what did help prompt me to submit two rationales:
Finally, I expect another reason why the timing may have led to fewer entries was because Future Fund applications were due 10 days later (that seems like a long time, but I know that its approaching deadline was on my mind when I submitted my rationales).