I've kind of come to that line of thinking ASSUMING it was sell higher PUT and buy the lower PUT, if so I believe they then bought the Jan 2020 $18 strike with the money. If all true it makes so much sense and something I would do in a heartbeat if I had the funds.
Basically as long as stock is above $12 at October expiry(with no stock moving news event on the horizon very conservative bet), you then get to have Jan 18 options for free where stock should be over $20 and likely around $25 but anything above $18 is your profit. If it is not above $18 you basically get a wash, no gain, no loss. $25 close and you make close to a million bucks.
I hope that's what it was, if so, I love when traders find these niches and can make large bets with minimal risk. Someday.....it'll be me!