Here's the earliest video I know of EQ, and it has a very M59 feel: https://www.youtube.com/watch?v=oFKrlynZNtU&list=FLrvKUlysHt...
EQ was the first 3D MMO.
UO was fantastic for its mix of PvE and PvP. For a time, you could be a player who preferred PvE but you could still protect yourself against PvP. I remember mining in rags, when underneath I was a fully maxed armed plate wearing mage ready to pounce on any unsuspecting griefers.
EQ took a different route, it emphasized PvE. PvP servers were considered broken.
There were endless discussions in gaming forums lamenting this lack of "forced but fun" PvP in EQ which was present in UO.
However, EQ proved to be more influential, the big successes that followed like WoW emphasized PvE and the care-bear factor.
Those games that tried to bring some sort of forced PvP onto users failed.(I am not sure where EVE falls in this regard)
Disclaimer: I played both UO(1998-2000) and EQ(2000-2006) and my bots still play EQ.
I think MUDs are sort of the genesis of most multiplayer online games, but there is some seed in BBS Doors as well (Legend of the Red Dragon etc...) that had some multi-player persistence.
Besides that, obviously pen and paper RPGs as well as fantasy adventure games (Kings Quest etc...) played a role in influencing all of these games.
For those who were around back then, there is zero question that many design decisions of EQ were chosen as a direct reaction to the state of things in UO and evolving customer tastes. Put simply, the average gamer simply was not (and still is not) ready for the sort of sandbox that UO initially provided, but a Diku on steroids was definitely in the cards.