Plenty of employers ghosting on applications and interviews. A couple of weeks ago I got an email rejection about a position I applied for last year. Sometimes, though, if you're in the second cut they hold you until someone is on board in case the person they want doesn't accept the offer. I know that hiring managers are busy and they try to screen for no more than the top 3, maybe 4, applicants. If you're #4 or #5, they might wait a while before informing you. Case studies are pretty much standard in my occupation at my level. They want to see how you think, how you solve problems, can you work with ambiguity and data. Most of the time when I've left a company it's because of the leadership and how I am treated than what I am doing (that, and them eliminating my position if not my entire department).