in terms of inertia, what is the disadvantage of a lightweight camera snapping the shutter?

Question

why is massive tripod preferred by most photographers

Answer 1

Less vibration. Inertial (aka mass) means an object at rest tends to remain at rest. For exposures using ambient (sun) light, if the camera moves by a significant amount during the time the shutter is open, the image gets smeared. The longer the exposure, the bigger the effect. This is one of the advantages of using a flash. The flash is very short and, therefore, it "freezes" the image, so the effect is very small, even if you don't use a tripod.

Answer 2

The focus of this question isn't the motion while the shutter is open, it's the motion imparted to the camera by the motion of the shutter. The camera motion is proportional to the ratio of the shutter's mass to the mass of the camera plus any rigidly attached masses such as a tripod. So the more massive the camera plus attached accessories is, the less the shutter motion induced blur.