Websites that sell DMA devices also sell devices that merge mouse usb and hdmi signals that allows you to run the cheat on another machine and let it display en ESP overlay and do aimbot. It's likely that a naive implementation of such an usb device would be detected. But can you create such a device that uses a normal mouse usb driver and looks like a normal mouse?

At least in Valorant, DMA is becoming impossible due to IOMMU / Memory Integrity enforcement. The only option is becoming pixel bots.

As for faking the input device: I'm sure it's possible, but I'm also sure that perfectly spoofing an input device is much easier said than done.

Even if it is possible, all they have to do is make it hard enough to where the percentage of players cheating is at the point where you will rarely if ever encounter a cheater in your matches. As far as I'm aware, Valorant is one of the only games that has accomplished that.