Actually this contract is not public, its source was not published on etherscan. You can read its opcodes and try to run it through a decompiler, but you can't

Actually this contract is not public, its source was not published on etherscan. You can read its opcodes and try to run it through a decompiler, but you can't get its original source. That shouldn't really matter though. The contract was not advertised to the public, he could argue it was a private contract that could only be used by whitelisted addresses. Sandwich bots made the mistake of trying to interact with a random contract and assuming that it follows a particular kind of behaviour.