'Why it is that...' vs 'why is it that...' (subject verb inversion)

Why (in the hell) it is that...?

Lupin III (1977) Lupin, Whom I Loved (Part 2)

Timestamp: 00:10:08

Shouldn't there be inversion of subject and verb here? Why 's it that...?

Yes, there should. It's a mistake which native speakers rarely make in speech (though some may in writing), but is quite common among people who do not have English as their native language.