Where did I go wrong

with my first attempt at shooting fireworks. I thought I would try the Scene Mode Fireworks to be on the safe side. Apparently it focuses to infinity ,sets the shutter speed to 4 seconds etc. I shot from a tripod with remote shutter release with my 40-150 lens set at 40mm at a distance of approx 100mtrs in RAW. Is the problem focus or too long an exposure?