I can't claim to be intimately familiar with Ukraine, but based on the US's history of funding the most violent psychopaths imaginable, I really doubt it's an accident.
I will also note that in the past, several elements of NATO's high command were former Nazi generals, so I really doubt there's a ton of angst about it internally.
Absent any evidence that NATO arms were specifically directed towards neo-Nazi groups (and not just groups affiliated with Ukraine's national police, which Azov unfortunately seems to be), I think there's nothing to support anything except it being an accident.
And again, this is from someone who exercises extraordinary skepticism in the context of US international action.
I will also note that in the past, several elements of NATO's high command were former Nazi generals, so I really doubt there's a ton of angst about it internally.