Sometimes the starting bid and timing of bids are very important.
The lot in May that got zero bids had a starting bid of $9.99; result no bids
The lot in June that got seven bids started out at $4.45; result 7 bids

The lot that got zero bids ended at 6:12 am when most folks are still asleep on a Sunday morning and unable to put in a bid?
The lot that was sold ended at a more reasonable hour (5:20 pm Sunday evening) and was bid up by three different bidders during the last minute by snipers. One bid was made at 17:20 42 seconds ... the next bid was two seconds later ... the final bid was made at 17:20:48 seconds.

Perhaps the item that was sold was perceived by bidders to be a better specimen than the one that received zero bids?

My conclusion is that besides the ending hour ... if an item is started out too high, nobody will follow it. If an item's opening bid is placed reasonably low, several bidders will watch it to the end. It's called competition.