The second question is clear, stars need some time to (apparently) move in the sky. The celestial sphere is rotating at 15 degrees/hour around poles (Polaris on North hemisphere) and the apparent movement is bigger near the celestial equator and smaller near celestial poles. But this movement is really a big problem if you want to take sharp photos of celestial objects, because ... they move! This effect is more pronounced with long lenses, and if you want to take a sharp photo of the Moon with a zoom lense you need to use speeds around 1/500.

The first question is more subtle to explain and I cant only imagine what could be happened. The Milky Way is a very dim object so using a long exposure may seem like a good idea, but the movement of the sky during that exposure time will produce a blurry image with a very dim light, almost invisible after enough exposure time. You have two options to avoid this problem: move the camera with precision to compensate the Earth movement (using a telescope automated tripod) or shooting with faster speed to freeze the movement on the photo, low f number to increase the amount of light that arrives to the sensor and use high ISO number to obtain more effect with this dim light.