5 Valor gyms wiped out.

I am guessing someone wanted to send a message without the recipient field filled out. Maybe some Mystic or Instinct player has a quarrel with one or several of the Valor players and decided it was time to pay them a visit. To avoid revenge actions, it seems that this trainer decided to leave no clue of his or her identity.

PS: When a player is banned, all defenders are supposedly left in gyms until beaten down, but I've heard that they are shown as "Player01" or similar nicknames. Would be nice if someone could confirm this.

There's pretty much 3 options -

1) Those players were cheating and were banned

2) The person who took them down was cheating and didn't want to leave evidence of who it was, did it for the exp and the lulz

3) Everyone was totally legit, but the person who took them down already had 10 defenders and wanted to do the nice thing by leaving them empty. (Putting in a dumb low CP Pokemon only hurts your own team by making it impossible to prestige efficiently and does nothing to slow down others teams)

My money's on #1 :)

Tough to say what exactly happened. If it is suspected that these Valor gyms were put up by cheaters someone may have said screw it and cheated as well to knock down the gyms but didn't want to leave evidence.

I will say this though. There is a guy in my city who drives around in a truck knocking down level 10 Mystic gyms every now and then but he doesn't put a 'mon in. Always leaves them empty. Kind of his calling card.

I did see him once put a 'mon in a gym and he's about level 35-6 player. He just drives around all night getting pokestops and stocking up on potions and then decides to take down a Mystic gym or 2. Thing is we always build it back up the next day.