Why was the The Citadel map very iconic in the Arena Shooter genre?

I do know the origins was from a Quake map. And I often see the map gets recreated in multiple Arena Shooter games.

I was still young when I played UT99, and UT2004 many years ago, and I don't know much about the development history, only now i started to watch a lot of documentaries and history behind Unreal and how Unreal Tournament was shaped to be.

But what's the history behind The Citadel map? Was it popular due to the competitive background? Was it a popular pick for a CTF map?