People in the Reddit top decided that they would run places again off-schedule. Best guess is someone thought that it would be good marketing for the coming IPO to show that Reddit is still functional with lively communities.
Any idiot could have seen what would actually happen coming a mile away. The only people who participated in r/place before are people who are now completely anti-reddit at the most and royally pissed at the admins at the least.
The bell weather was that Spez couldn't stay positive in that ama. Even with manipulation, they can't beat the overwhelming number of users. It's astounding they thought different here.