Graphite is good conductor of electricity because one carbon atom is bonded only three carbon atoms, which enables the presence of free electrons. In fullerene 60 the carbon atoms are also bonded to three atoms so why is fullerene concidered a bad conductor of electricity?
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.
The sheets in graphene basically extend all through the entire material; you essentially have one macroscopic orbital going from one side of a pencil to the other. Push an electron in on one side and one will come out on the other. Great.
In fullerene, however, you have distinct little footballs that are just lying next to each other. You can easily push electrons around within one football, but it’s hard to get them moving between footballs. You would need to push them from one end of your material to the other, though; so it doesn’t help that they happily circle their football.