Simo's hair might have been a contributory factor, as the bulk of it may have led to him needing a larger size, and hence while being perfect for "normal" helmet use, meant that under the impact he suffered, it simply came off.
Yes, those were easy to identify, the Ratzenburger/Senna point being raised earlier anyway. There are others, but it took 10 seconds to think of those, and they were enough to make the point.
I could list more.
Making the helmets more secure would affect more than just the likelyhood of decapitation, although that would be the main risk.
doing that would have to require stronger necks to cope with the forces involved, and to do it articially would reduce the riders control in some way, no matter how you tried it. You can do it in car racing because the neck doesn't move, it just needs to be stronger to cope with the lateral acceleration.
Wait for the inquest that will have to come out eventually.
Improving the tyres would take a whole lot of effort, and making them giveway straight away would be a bad thing to do, they need to be providing feel of what is happening with the track, not taking it away.
I agree, there is always more that can be done, but the easy way out is to stop racing, and people don't want that.
Considering nearly all of the track fatalities have involved more than 1 person, why not make everything a time trial?
That would be a easy way out, but would spoil the show, and, since this is a entertainment based thing, that would lead to no racing eventually, as the money goes.