Why is fullerene 60 an insulator while graphite is a conductor?
To reiterate Ivan's comment fullerene is a bad conductor because that's what the measured properties produce as a result. The mechanism that makes it a bad conductor is that it has shorter range continuity than graphite. In graphite the carbon is made of sheets that can be as long as the sample. These sheets have fairly low conductivity, but when the electrons must jump between sheets to continue its path, this is when the conductivity value for the bulk material lowers. Extrapolate this to fullerene. If the fullerene molecule itself had high conductivity, it would still require the electrons to jump between molecules every few nanometers. This can produce a rather large resistivity for the bulk material much more so than observed in graphite.