Monero mining is a lot easier to hide
-No crazy heat, energy draw, or noise
-Can mine on general hardware and "blend in" (everyone knows what someone is going to use an ASIC for)
-No major pools that require KYC and are over 51% of total hash
Why would it become centralized just because criminals mine it? There are many factions that make up "criminals" would be competing along with everyone else that mines