Firstly, its hard to say whether it actually hit a Crusaders player directly, or glanced off a Lions rucker first. There is no camera angle showing it from behind the Crusaders side of the ruck (which is what we really need)
Secondly, Even if it didn't hit a Lions rucker first, the Crusaders player in front didn't play at the ball, so its not a penalty, its accidental offside. Scrum Lions
Thirdly, it happens so fast (like pinball) that all the officials missed it (not clear and obvious), and that is backed up by the fact that it has taken nearly six days before anyone has noticed.
ETA:
I've just looked at it in youtube using the super slow-motion setting.
The ball cannons off the front leg of Bryn Hall, sideways onto the back leg of Ryan Crotty who is slightly in front. The ball doesn't obviously go forwards from the first player, so its a tough call to say this is offside. Imagine a situation where a player offloads the ball from way out in front of him, and the ball travels backwards or flat to a player who is slightly ahead of him but who has to reach back to catch it. You'd be a real jobsworth if you called that offside.
NOTE 1. Tamanivalu may have been slightly ahead of Hall, but Hall wasn't the last team-mate to play the ball, Crotty was, and Tamanivalu definitely wasn't ahead of him.
NOTE 2. The nearside AR has a perfect view of the whole thing. He was in line with the two Crusaders players. That is South African referee Marius van der Westhuiizen who is well known for sticking his oar in at the slightest provocation. He says nothing.