This verge article[1] lays out some of the timeline, and it seems that even a week after the investigation opened Elon tweeted about how at least a green card was required[2]. At best it feels like they were not interpreting the law in good faith.
No, you're right, it could also be years of ignorance from multiple levels of SpaceX combined with an obstinance to not consider changing their position even in the light of a federal investigation.
