I disagree with anyone who claims they can pinpoint the reason why people stopped playing, Greifing wasn't even the largest reason people stopped playing and a quick look at steam reviews can confirm everyone has their own reasons. Every player is different and every player has their own breaking point. Weather it be greifing, price, grind, graphics, security issues, bug, exploits, cheaters ect, ect.
The reason I stopped playing after all this time (7 ish years) is my enjoyment came from the struggle of building myself up from nothing and competing against others on many different aspects (combat, wealth, TC, guild prowess). At some point the joy of doing that was lost and I can't really remember why. Maybe the lowering population, after all theirs's no point striving to be a king when the throne you covet is in a competition of so few.
The reason i won't be playing MO1 while I wait is because ill be playing MO2 alpha, I want the game to truly succeed its predecessor. I want to find and test and suggest as much as I can to make the next installation better. I can't do that if I'm playing MO1, or at least not as well. This game will suffer the same issues of the first such as the problems I mentioned above, however as a community testing and giving feedback hopefully we can lessen them.