This may have to do with the themes the movie explores (a viewpoint is explained in this great answer) but it remains a question to me nonetheless.
The soundtrack made me uneasy. This was not a normal inspirational movie where a nobody becomes an important and influential person, it's about a nobody who becomes an influential person by having his assistant and probably his competitor murdered, killing empathy and morality along the way.
It may have been a satire on media but it never glorified those actions. In several scenes, Louis does some unethical things bordering on illegal (just as far away to absolve him) but the background was playing some upbeat this-is-an-inspired-LA music.
Why is Nightcrawler's soundtrack so upbeat? It's from James Newton Howard so it goes without saying that he knew what he was doing.