One of the reasons it has remained popular, is that the play is enjoyable simply by itself and though it was originally particularly appealing to the public at the time who were very familiar with the various political factions, etc., it has remained more popular (perhaps) than the others because of its stand-alone quality even without historical or political context.

The character of a king who plays a very humble role while at the same time harboring expansive ambition to rule is a very interesting and useful character, some even say soap opera-ish, clearly maintaining its appeal throughout the history of the play's production.  There is quite a lot of family drama, intrigue and betrayal, all kinds of great stuff that audiences can sink their teeth into regardless of their knowledge of the historical context.