Most probably internal issue within the company between the hiring manager (the one that want the vacancy to be filled in), HR and management.

It is quite rare for HR to move on to discuss & finalize salary, benefits & other terms if the hiring manager did not give consent.

Probably the hiring manager gave consent and go ahead to hire, HR do their stuff and then suddenly the management or higher ups disagree with hiring manager's decision. This led to another round of interview (which you had to attend).

Just move on to the next/future interview. Don't bother with their internal mess.