They're very similar, but slightly different.
'To crash' is generally used to describe the thing moving at a high speed, while 'to smash' describes the person or thing doing the breaking.
For example, if I smash a glass with my fist, then my fist crashed into the glass. 'Crash' sounds a little unnatural in this example, just because 'to crash' is usually only used to describe vehicles or things moving at a very high speed.
It's possible for something to crash into something else without smashing it. Something only smashes if it breaks violently into smaller pieces, but 'crash' only implies that the moving object slammed into something very hard.