I think it's possible that, like with Heller, the court picked a particularly ridiculous and unusual law so that it could make a foundational ruling about the scope of the Second Amendment without radically and suddenly shifting the legal landscape. They know how important it is to not move too quickly if they want their rulings to stick around and not generate too big of a backlash, especially in the current political environment.
That said, obviously a "bear" case should have been taken up back in 2012 or so, moving with cautious but deliberate speed. Clearly the problem was Kennedy.
The standard of review is a separate issue that is very unlikely to need to be decided in this case, because the law is so stupid it fails any form of heightened scrutiny.