The definition of a Trojan is malware disguised as legitimate software designed to cause harm. It's safe to assume that while cracks can be Trojans, not all of them are. Only cracks that generate malware can be called Trojans. I'm pretty sure that crack tools are detected as malware or viruses because, by definition, they are.
Its specific purpose is to modify programs and files so that they do not work as designed. They delete the verification files, modify the state of the registry, and do everything they can to prevent their target from working as intended. Cracks can sometimes do virus-like things, leading to false positives. We can see that the decrypted software contains malware and also the social engineering skills used by the hacker by which the hacker can hack the person who downloads the decrypted software.
I know that part of the crack is a fake file to lock your computer or steal private information, but most of them can make the software run in full version. I downloaded this RAT since it is a decrypted version, but I wait a moment and I think why someone would give some free payment and decrypting a software is not that easy, since it requires a lot of patience and knowledge, and the time to decrypt a software can take hours and even days. Other than that, decrypted software can infect your device or make it more vulnerable to future infections. Often, the person who installed that software and manages it wants to know that decrypted software has been installed on their machine.
What I'm trying to say is that just because a crack seems to work well, you shouldn't sit back and relax. If the anecdotal reports cited by Avast were any indication, the cracked games played well, only with a little more invisible threat. I tried to run the crack in sandbox or use some online service like FireAMP to analyze what file, log is created, but usually there is nothing suspicious. Crack is adware software that delivers advertising content to the end user and can be considered invasive of privacy.
Cracks that are also Trojans are particularly dangerous because the hackers who created the malware will not only want it to enter your device without being seen. It is not uncommon for known harmless crack signatures to be permanently blacklisted by antivirus software, even if those cracks do not infect your devices and do not collect personal information. The scrolling is identified and the code is manipulated to jump, regardless of which serial key is entered, which decrypts the game. That's why they will make sure that the crack works as intended on the surface so that you have no reason to try to get rid of it soon after installation.
Technically, all you need to decrypt a software is a text editor that can edit hexadecimal values in a binary (Hex editing software is suitable for this).