The pavement is most the difference I think. With the 156 turns, I think the instant torque is a huge factor. The altitude certainly has an effect, though I believe the FI they are running mitigates much of that.
That depends if you mean Forced Induction or if you mean Fuel Injection with FI... In either case there is still power lost with altitude and with Normally Aspirated engines it is a pretty significant power drop off. With Turbo and Super Charged Forced Induction engines the drop off isn't as bad but it is still there for sure. Since virtually the entire course is run at altitude and keeps getting higher it has a huge effect on the power the cars make while running up the mountain. Even with Forced Induction it takes a lot of fuel delivery to still make power at altitude.
No doubt the electric motor's torque is a factor, but don't discount the altitude. Again the paving of the course made the biggest difference in reducing times. Each time they added a new section of pavement the record times dropped significantly, while on same course conditions records were very close to the old times when/if they were broken.
