Williams Entertainment, the company behind the Doom PS1 ports, were apart of a larger company called WMS Industries, which also owned Midway, a gaming company you may have heard of. Towards the end of 1996, Williams Entertainment was renamed to be apart of the Midway branding, which is why the same team as those PS1 ports made an original Doom game under a completely different studio credit.
It’s still the same guys, mind you, and they had been working on this particular game since 1994 with guidance and final say from Id Software, if you can believe it. It was under the working title of The Absolution, which is a fantastic title that for one reason or another got the much worse title of Doom 64. This caused confusion as a lot of people, for a very long time, had no idea this once N64 exclusive was a completely original Doom game, a direct sequel no less. It was assumed to be a port just pointing out that it was the N64 version, but it is much more than that. Doom 64 is a unique creature in the Doom franchise, with a mood all its own and with some fun new elements that had never been seen in the franchise until now. Some would even argue this to be the real Doom 3, and yeah, the fact it’s a direct sequel and not a reboot would make it a proper Doom 3.