Why do some gamma-ray bursts look weak in X-rays?

BeppoSAX detected 96 gamma-ray bursts, categorizing 38% as X-ray flashes (very soft), 42% as X-ray-rich, and 21% as normal bursts. Despite similar spectral slopes and afterglow rates, the key difference is peak energy: X-ray flashes peak at 8.5 keV versus 83 keV for normal bursts. This suggests a single class of objects viewed at different angles or with different jet properties, not fundamentally different events.