As you pointed out correctly it was not as big. Yet fitting 17000 into a 10000 capacity was never going to be safe.
I've been to Hillsborough not sure if you have. It would have held about 47000 if memory serves me right.
Forest would had maybe 20000 Liverpool maybe would had 27000 tickets.
Over 50000 Liverpool fans turned up that day.
Even then Hillsborough was antiquated shït hole. Never was it geared up for such numbers, in or outside the ground.
A big difference is that when the disaster happened, the Leppings Lane terrace wasn't even full. The fatalities all occurred in the two central pens. There was still plenty of room in the pens on either side. It was a failure to properly control and direct the fans that caused the disaster. If they had closed off the two central pens when they were full, like they did the year before, nobody would have been injured, let alone died.