How Was John Byrne Able to Reboot the Doom Patrol?

[Timothy Hunter]

I am currently reading Chris Claremont, John Byrne, and Jerry Ordway's arc in JLA, the Tenth Circle. On it's own merits, it's a great storyline, but put in the context of the wider DC Universe, it raises some troublesome questions.

In the Tenth Circle, the Doom Patrol debut as if they were a new team: Rita Farr is still alive and well, Niles Caulder is back to having red hair, and the Justice League act like they've never met the Doom Patrol in their life.

So Chris Claremont and John Byrne controversially wiped away all previous Doom Patrol stories from continuity. How was this accomplished? It would make sense if this new Doom Patrol were introduced in after universe altering events such as Zero Hour or Infinite Crisis, but they weren't. Was there an explanation given to justify this change in continuity?

Was Byrne's Doom Patrol erased from continuity after Infinite Crisis? This would make sense because there were references made to the Morrison Doom Patrol in the pages of Geoff Johns' Teen Titans. Did Keith Giffen's Doom Patrol ignore or elaborate upon Byrne's run?