The telescope received minimal funding because stakeholders couldn't make a good case for more. The results the facility could produce weren't seen as justifying the expense. In that light, that it was operated at all was more than one might reasonably have expected. The alternative was to just shut it down earlier. They squeezed the last drops of output before the old thing was allowed to die.
Sometimes with facilities like this you have to make the call that it's over.
Budgets are limited and there was cooler science to do in space and the newer more modern (and in one case even larger) ground-based ones.