I think many of you are confusing the composite popularity of each individual Wu member with their success as a singular group called The Wu Tang Clan. Bone was just as influential and actually sold way more records in a shorter span.
Now of course in popular culture, Wu is referenced, played, covered and altogether probably more relevant than Bone, but that's on the surface. Part of the reason Bone's shelf life was so short (along with their personal demons and lack of appropriate representation after the death of Eazy) is that people started to mimic what they did. If you think Wu Tang's style has been bit on a Hip-Hop level, its nothing compared to whats happened to Bone on a Pop and R&B level in the late '90s heading into the millenium. Once Mariah mastered the 'Breakdown Flow' (Krayzie) she added that cadence to her arsenal. Same with Beyonce who's basically a rapper with a singing voice who started off mimicking Bizzy's harmonies way back on the first Destiny's Child album(see Wyclef interview about No No No; see Second Nature using same sample as Crossroads) and has gradually developed her own 'flow'. Bone wasn't really able to capitalize off this because there was no RZA to serve as the gatekeeper to the sound, it was something that once the code was cracked could be somewhat replicated. Not that other producers can't make a RZA beat, but that Wu was able to own and brand their sound.
20 year's later you see the influence in ASAP Rocky, Future, Kendrick as well as others. Wu has influenced a great deal of artists as well, and both groups are responsible for a lot of the slang we still use today. I think a better question may be 'What stopped the members of Bone from having as much individual success as the individual members of Wu' but solely as a group, I think Bone is right there if not surpassing Wu as a group.