There are a few benign-ish ways this happens, based on my experience from working on “the other side”. They reflect shittily on the hiring manager, but not on you:
You got no immediate rejection because they did consider you valid for the position, just not first place. Then they got a match on the first place and stopped giving a shit about the applicant backlog.
They got too many applicants and threw half in the garbage.
Upper management put a freeze, or reduction, on hiring right as they put an ad out.
They have a person already picked for the position, but they will get in legal or corporate or PR trouble if they don’t pretend to do a proper hiring process.
Their application process, human or computer, lost your CV.