Why did the SRA allow the order for 9 car 222s to take place, in the knowledge that they would be run to Leeds?
As I understand it, they later backtracked; why?
I think a bit of context and background info is needed here! Many people will be unaware of what was proposed!
Basically as you say the SRA originally planned for there to be a frequent (presumably hourly) London St Pancras - Leeds service, but that didn't happen. It's not clear to me whether the trains were originally intended to be routed via Derby or Nottingham.
Instead, several years later, it was finally decided to run a separate Nottingham-Leeds service, which ran as an extension of the then relatively newly introduced Sheffield-Leeds fast Barnsley service.
I think that having this as a separate service (most of the time - there are, of course, some through trains) makes more sense, as the loadings between Nottingham, Sheffield and Leeds are typically going to be lower than those closer to London.
As for why they "backtracked", I assume it's because they ran out of money?