Just thinking about the stranded 333 last week, & without trying to be an "expert", but it was I believe Leeds bound & stuck between the downed wires at Armley & the loop at Kirkstall. Add to the maybe at least another couple of units that rolled up behind it before the word could get out to stop all Aire & Wharfe services, and you are left with at least a couple of units without power & stuck on the wrong side of the incident depot-wise. So really its not hard to imagine that trying to organise either getting units back up west away from the incident, or trying to get a rescue train to the original from Leeds or Neville Hill would have been a challenge to say the least. At best there might have been a couple of DMU units on the "right" side of the incident, but they presumably would have to wait until all other services were cleared out in front of them before getting down to Armley. I imagine Northern had to wait until engineers could clear the wires & allow safe working past the incident to get any rescue train out from Leeds? If so, then it is not surprising it took the time it did.
Maybe a line evacuation might have been an option, but where the stranded unit ended up isn't a great place for an evac. A deep cutting with wires down ahead, and a fairly remote area behind when it comes to access to a road, or maybe canal. And in less than ideal weather conditions, being damp & foggy in Leeds as I remember, it could have been more dangerous to risk that than wait until passengers or the unit could be moved.
It reminds me of an incident many years ago when the 333 I was travelling on hit a person on the line just east of the Thackley tunnel. With the driver unable to continue driving due to shock, and the train stopped in an area surrounded with fields in pitch darkness, there was little choice but to wait for the emergency services, the engineers & a replacement driver to make their way to the incident, which basically was across very muddy fields. So we were stuck for the best part of 3 hours until everything was in place for us to continue. Of course had we waited long enough, a mile or so down the track a new station would eventually have appeared to maybe allow an evac, although I suspect no-one would have been allowed onto the ballast until all evidence of the unfortunate soul were cleared away. Sadly, no matter what contingencies are in place & triggered in any incident, circumstances can render them useless & you have to apply plans 'B','C' & 'D'.