Well AoE 2 had 2 undisputed advantages:
1-It captured most of the already existing AoE1 fanbase while adding plenty of new fans (I feel most people that played AoE played AoK as their first AoE agame) and
2-With the testing that was AoE1, gameplay wise, AoE2 is a much better rounded game (even I have to admit it), that fixed many of its predecessor lacks and excesses.
Maybe 2 other things helped for at least fans (I personally don't like either of these)
1-The historical period
2-The graphics
[This message has been edited by Suppiluliuma (edited 04-04-2021 @ 02:00 PM).]