If objects don't move when the universe expands, how can the expansion result in redshift?
The redshift is indeed not caused by the movement of the objects, but by the expansion itself. This is a theoretical result from considering the FLRW metric for a light ray traveling on a null geodesic.

A derivation can be found here.

The cosmological redshift $z$ is given by $z+1 = 1/a$, where $a$ is the scale factor (the size of the Universe) at the time the light was emitted. Notice that this result doesn't care how the Universe expanded. In principle, you could imagine a universe which was static when the light was emitted, and static when the light is observed, but expanded by the factor $a$ at some point in between, and you'd observe the same redshift as if that universe had expanded gradually in the meantime. This is in sharp contrast to a normal Doppler shift, where in such a hypothetical case, the would be no observed redshift.

Note also that galaxies receding faster than the speed of light $c$ is no hindrance for us to see them; all galaxies with a observed redshift larger than $z\simeq1.4$ recede faster than $c$. The most distant observed galaxy GN-z11 has a redshift of $z=11.09$, and recedes at $v\simeq2.2c$. When it emitted the light we see, it receded even faster, namely at $v \simeq 4.3 c$. See the ant on a rubber rope "paradox" for an intuitive explanation.