The fact that an old question can reappear and get new answers is by design. Things change, what was the best answer a year or two ago might not be any more. Admittedly this is less likely in the world of DIY, but it can still happen - especially if electrical codes change.
I too get thrown sometimes by old questions reappearing - they might have been ...
As noted in the other answer, the OP had over 160 rep at the time he created the bounty, so a 100 rep bounty was within the rules.
See the FAQ on [Meta Stack Overflow] for more than you ever wanted to know about bounties.
In this case, the bounty expired about 7 hours ago as I write this. The person who created the bounty has a 24 hour grace period to ...
It's incorrect to say that a 65 rep user set a 100 rep bounty... a 165 rep user set a 100 rep bounty hence he became a 65 rep user :-)
See the rep timeline here: https://diy.stackexchange.com/users/15889/greg-smalter?tab=reputation&sort=time