Things were already moving in that direction though. Many games used Doom / Quake / etc engines in the 90s I think the turning point came when the work to writ

Things were already moving in that direction though. Many games used Doom / Quake / etc engines in the 90s I think the turning point came when the work to write a new engine became greater than the work to use an off the shelf and make it your own. And that only came about as people's expectations for physics, lighting, etc got pushed ever more.