Well, I have a theory.
The gunman was crouching right at the grassy knoll in Villeneuve curve. The bullet impacted the helmet, ricocheted from it, and cut the data lines. Then ricocheted a second time and broke the suspension arm that finally hit the visor.
Senna sensed the first hit before the arm broke, so he inclined his head to watch the suspension.
However, there was a second gunman hiding in the ARMCO barrier at Traguardo curve. His bullet was the one that hit the base of the skull. The bullet was shoot from the back of the car but hit the helmet right outside its edge, in the base of the neck.
Illuminati don't spare money on assasins. Ergo, it was Mosley.
The motive?
Senna has promised to devote all the money from the ASF foundation into looking for the Arch of Covenant. The Nazis kew it and they were afraid of the superhuman powers of Senna, so they put a Mayan crystal skull piece inside the helmet. This kind of Mayan magnet, of extraterrestrial origin, attracts lead, as everybody knows.
That's the reason why the bullets were attracted by the helmet, explaining why the gunman (and his accomplice) targeted Senna so easily at top speed.
The accomplices at Williams, a retired KGB doctor and a mechanic who has worked for STASI industrial arm, who participated in Stalin's purges, were able to hide the piece of crystal inside the helment before the race and retired it the confussion following the accident.
This same piece of crystal magnet was used by Mosley to hypnotize delegates into a vote of confidence this very morning.
Clear as crystal. This means that Rubython is a trustful source.