Stimulus isn't a switch you flip on and off. The idea that if you flip it, and the economy doesn't take off then stimulus doesn't work, is not a sound idea.

You can have stimulus in different forms, different points of time, and different levels.

So why would continuing policies meant to help? Because discontinuing them would have a significant detrimental impact.

Based on this point of view, stimulus and monetary policy have no effect, so the financial crisis should have been left to run its course. That would have been a terrible outcome, and we would be worse of than we are now.