The reason for ice molecules to form a hexagonal crystal structure is related to the bond angles in the molecule but not necessarily the way you think. Ice has a whole bunch of stable phases at different temperatures and pressures, at our common temperatures and pressures, hexagonal is dominant (but not exclusive). It's a gross simplification to say 120 degree bond angle = 120 degree crystals - many molecules have defined bond angles that doesn't really relate to their crystal structure.
i.e. silica in quartz which has a very defined 144 degree bond angle so forms these really clear tetrahedra on the molecular level, but the coarse crystal structure is a kind of skewed square, related to the hexagon. If you increase the temperature the tetrahedral are basically unaffected but the crystal structure changes significantly.

The hexagonal crystal structure is very very common because it is a "close-packed" structure, so it is thermodynamically favourable in a lot of situations, including in some carbon allotropes.

My field isn't really minerals like ice(more of a metallurgist) so sorry if this isnt super clear, maybe a geologist can weigh in a bit more. Metals are a good example of how bond angles aren't too important in crystal structure, they don't form "molecules" as such, so there isn't any define angles between atoms exactly(e.g. In liquid form), but they still have very defined crystal structures as solids