Emulators have always existed alongside their consoles. That’s to only way you get enough talent involved in a project like that. Difference is these days computers are fast enough to emulate the consoles much better and the architecture they use is a lot closer to what the PC is using anyway in a lot of cases, or at least a documented strain of ARM with a few custom tweaks.

The people working on the emulators are pioneers forging a path that takes a massive amount of time and effort. Trial and error, tweaking and ironing out the kinks can last years.