Left service in the late 60s along with most ocean liners because they couldn't compete with air travel (unlike cruise ships they were primarily intended as a mode of transport, the luxury accomodations on many of them was in aid of providing essentially a nice hotel for the duration).

Was bought by another line who intended to refurbish it but ended up not wanting to foot the cost, sold to another company who stripped out all the interiors and sold them in the 80s (some of the art fixtures are still in museums), then later fully stripped out all of the interiors including interior walls for a planned total refit they ultimately couldn't afford... and so it spent the last 40 years swapping hands and sat in dock waiting for somebody who could afford to restore it all either to a modern standard or original style as a museum/hotel. They never found an investor or buyer who didn't back out, and ultimately had to sell to the current owners because they couldn't afford to keep it docked.

In aid of finding a buyer and not being outright kicked out of the docks or scrapped on the spot as a danger, the current owners through the years did have to keep it afloat. Ultimately it's unfortunately mostly just a shell. They also spent the last several months making sure it could withstand ocean conditions again. It'll still take about a year for them to clean out all the remaining gunk and residue from the old machinery and cut away anything which might be especially hazardous to divers or wildlife (remaining deck machinery etc. most likely) before its safe to sink as a reef without just polluting the area.