harry potter - Why did Snape want the Dark Arts job?

There's a lot of talk about why Snape was denied the Defense Against the Dark Arts teaching job, but why did Snape want it in the first place?

He is shown to be very skilled at two branches of magic: Occlumency (enough to resist Voldemort himself) and Potions (as a student he figuratively and literally wrote the book on the subject) - and his attitude in the notation in the Potions textbook implies he took great pride and enjoyment in his Potion skills in particular.

True, he had an interest in the Dark Arts as a student, but surely he realized he would never be able to do "Dark Arts research" just by holding the teaching post (also, per JK Rowling Why did Snape love dark Magic so much?, Snape was interested in group membership more than the Dark Arts themselves). Furthermore, it was subtly implied that he lost his interest in the Dark Arts after he lost Lily because of them. Finally, Harry's favorite subject was Defense Against the Dark Arts, and as petty as it is, Snape maintained the sort of pride that would not enjoy pining for the teaching position that was Harry's favorite.

So why would he want the job at all?

Answer

'The Dark Arts,' said Snape, 'are many, varied, ever-changing and eternal. Fighting them is like fighting a many-headed monster, which, each time a neck is severed, sprouts a head even fiercer and cleverer than before. You are fighting that which is unfixed, mutating, indestructible.'
Harry stared at Snape. It was surely one thing to respect the Dark Arts as a dangerous enemy, another to speak of them, as Snape was doing ith a loving caress in his voice?
'Your defences,' said Snape, a little louder, 'must therefore be as flexible and inventive as the Arts you seek to undo. ...'
_{Harry Potter and the Half-Blood Prince, Chapter Nine - The Half-Blood Prince}

It seems pretty clear from that quote that Snape both loves the Dark Arts themselves - hardly news to anybody, I imagine, especially considering he (to quote Sirius, I think it was) came to Hogwarts knowing more Dark curses than most seventh years - but also the unique combination of skills required to combat them. He also seems to place a premium on branches of magic that require more than memorisation of incantations and wand movements (Charms, Transfiguration) or even seemingly very little actual magical ability (Divination, Care of Magical Creatures, History of Magic).

He expresses a similar view about his previous subject, Potions:

'You have no subtlety, Potter,' said Snape, his dark eyes glittering. 'You do not understand fine distinctions. It is one of the shortcomings that makes you such a lamentable potion-maker.'
_{Harry Potter and the Order of the Phoenix, Chapter Twenty-Four - Occlumency}

Since being successful at Defence Against the Dark Arts requires that you be "varied and ever-changing", I can easily see him viewing the subject as the pinnacle of magical ability (there's a reason that Aurors are considered "the elite" and very few Hogwarts students are accepted into the training), and thus gaining a huge amount of satisfaction from being the one in charge of teaching it.