Why would they? It's Iran. Not anymore the song "We're all living in Amerika" is true.
But how would you prove that huawei (the corporation) was spying? I'd imagine that you would need proof that it was officially sanctioned within the organization, at multiple levels. Since spying is illegal, you'd expect that if they were spying, that they'd be doing it in a way that generates plausible deniability for the higher ups. So it's not surprising at all that all the criminal charges so far are for employees acting on their own accord (or at least appear to be).
Should we apply some different criteria of guilt based on origin?
edit(charged->found gulty)