If this is the end of its life I presume it will either be approaching a Fatigue or Creep failure. Both of these occur over a long period of time and should have been noted during off season checks as not being able to last the year. The fact the ride has been closed now shows they are monitoring for these failures, so they must have spotted it before. It was foolish to wait until it passed the safety margin before deciding the cable needed replacing.
I second this, they would have known that the cable was very much near the end of its life span, and would almost certainly be able to tell in the closed season that the cable wasn't going to last the season. Due too the slow nature of fatigue and creep failures its almost certain that the cable would not be in much of a worse state now, if any at all than it was in the closed season. The cable is probably still useable, just its not worth the risk.
But it could of been a case that they were not able to get a new cable manufactured in time for the new season, and therefor decided to operate the ride for as long as possible into this season before it was deemed unsafe to operate, which is very much feasible to be fair. As Diogo said, they dont usually have these things lying around, seeing as every single cable car in the would would require a different length of cable.