I don't think there's been any particular rise in neurotypical diagnoses...
But anyway, yes. It comes down to three things:
1 - The realisation that Aspergers and autism are, at the root of it, the same thing.
2 - The realisation that the tendency to hide the condition in order to function in society (ie masking) is, by definition, a part of the condition...and that previous diagnostic tools were incapable of dealing with that.
3 - The correction of misdiagnoses like bipolar disorder (especially in women) which were incorrectly medicated, when they were actually autistic (but the medical profession didn't believe girls/women could be autistic).
Everything else is just a consequence of those things. Particularly #2 - while it used to be that only children were diagnosed autistic, the reality is that there are multiple generations of autistic people in out in the world trying to cope with life in ways that we shouldn't have to, and with the reduction in the social stigma attached to it we're finally able to be heard...and we're talking about it, rather loudly. It's a very isolating condition, and those of us who were early-maskers grow up believing we're the only ones that are weird like this, and hide it for fear of becoming outcasts...so just knowing that there are others (a lot of others) out there like us means that we don't have to do that any more.
The result of that is a perception that there's some conspiracy to over-diagnose it, or some other such social phenomenon, but that's really just a distortion of reality. Every study that's been done shows that adult diagnosis
So, basically, this "absolutely massive rise" is a one-off correction. It's no cause for concern, but it deserves recognition.
Autism has been in my family for seven generations, and members of my family were subject to everything from being called the village idiot to being institutionalised and destroyed with drugs and ECT when the reality was that they could've had long, happy lives if we knew then what we know now.