How malware can detect other malware?

I'm trying to understand how malware's can detect other malware's on a any PC.
For example we have a certain machine that has just been infected by a RAT #1, before that there was already some kind of miner / RAT #2 on this PC, how a newly arrived RAT #1 can detect these old competing malware's and remove them to remain the only RAT in the system
(no need to use any API VirusTotal, AVCheck and other similar sites, …

can cybersecurity detect kind machine malware miner rat understand