There was no All-hands Puzzle for a long time.
Maybe the developers were disappointed with the results.
In my opinion those results were caused by the procedure of automatic regular sharing, that just led to many very small improvements of only one or two good starting positions. There wasn't many big moves, large rebuilds or experiments.

I think if you want to get better results from all-hands you should change a few things:

1. At the start there are a few different public shared solutions (you don't have to change that)

2. Set a 24 hours countdown at the start of the puzzle (don't set a fixed expiration date and time)

3. Every time someone uploads a new best scored solution, the countdown will be reset to 24 hours

4. You have to share to the public manually to get your score credited

5. There is no automatic sharing of solutions to the public