3 rounds of interviews and HR says to sit tight on two occasions - what's the deal?

So, I'm a little confused by my situation. Had three rounds of interviews (9 in total) across 4/5 weeks. All went well and I was down to the final 3 candidates for the role. I did my final interview two Wednesdays ago and the firm finished up on the Friday.

I didn't hear back until the next week (Thursday) and this was simply HR saying to hold tight since the interviewers have not had a chance to discuss the final 3 candidates and it could take a week to hear back.

Another week passes (all of last week) and then HR reaches out today to apologise for the delay again and say that I'm still in the running. The HR lead says that she anticipates a decision being made in a couple of weeks. HR said that she is happy to discuss further but I'm unsure if there is anything to really discuss?

My first thought would have been that they are interviewing more people and trying to keep me 'warm' but the process was so long winded. It could be that they are waiting for someone to accept the offer, but two weeks seems like a really long time for that?

Any thoughts would be appreciated..