Wanted to ask, given the latest puzzle and last couple of solved puzzles are unprofitable to crack by renting from, say vast.ai or clore.ai, what do you guys think these people who cracked last couple of puzzles rented those 1000s of GPUs?

Current prices say they should spend around 1.5 million usd to crack 6.9 btc puzzle which is not at all profitable. So, how are they doing it? Stolen/hacked GPU compute?