A molecular bond between two atoms vibrates with different amplitudes depending on how much energy it has. It is found that the low energy vibrations are more likely than the high energy vibrations. Why?

It is similar to how balls roll down hills to lower their energy. There is more space at the bottom of the hill than the single point at the top.

Once a molecule moves to lower energy the released energy is gone and cannot come back.

When the bond has less energy the extra energy can go to many other molecules

Molecules with less energy can be in more microstates than molecules with more energy.

There is usually another molecule that needs the energy more.