I probably wouldn't have pushed it either to go on to the county fair. It would have been a big leap for me to assume why certain projects were chosen and others weren't. Since he really wanted to go on, you had another avenue and took it. I'm surprised the other lady didn't leave it alone as well.
Most of the projects at my DD6s fair at a small private school were demos vs actually attempting to answer a question. Some judges like to see things hand-written vs electronic and assume powerpoint help was given by parents whether that was the case or not. There were many interesting projects and it had to be tough to judge. Last year DD6 (then 5) continued on, this year she didn't.
At DD11 district science fair, I saw such a variety of projects I had no idea how they judged. At her school fair, where she got interviewed she won 1st in her category. At the district with no interviews, she got honorable mention (ie 5th place? maybe). The boy she beat at her school got 1st. So it's really just a crap shoot.
I've tried to just tell them any time something is "judged" subjectively you just never know and just to deal with it.
FWIW I learned this lesson via roller skating at an early age, maybe 5-7. And yes I was in tears at one point because of the fairness but I came back and made sure there were no questions the next time. I'm not sure with a bright kid that 7 is too young to talk about it. Also FWIW, I'm a scientist and this is why I HATE science fair even though I love doing experiments. The dog and pony show never appealed to me.....
