Your PIR output device is probably a triac, so there's a snubber across it. It's likely to be of the order of 0.47 µF in series with about 220 ohms. You loaded the output so that the leakage doesn't trigger your load.
A triac feeding a transformer can be dangerous. It can trigger on half cycles, resulting in DC, damaging the transformer. Fortunately your 60W lamp also resolves this risk.
If you want to avoid this problem in future installations, use only PIRs that state that they can be used with fluorescent lamps. These have circuitry (usually a relay) that has little or no leakage.