They clearly did think a fine was enough - they didn't rule that in future cases points would get docked did they?
The tribunal was not about overruling the FA's decision so why would they?
They were making a ruling based on whether Sheffield UTD deserved compensation because they were relegated.
Please note, If west ham were given a points reduction sheffield utd would not have been relegated. This is important when considering the context of the ruling, and the amount they recieved in compensation (almost 1 whole season of premiership tv money iirc). It was clearly felt by the tribunal that Sheffield UTD were relegated unfairly. This ruling will be taken into account when considering future punishments for cases of a similary vein.
The difference here is that there was actually some subterfuge involved as well. It's actually an even more serious case than what West Ham did.