HI I WOULD LIKE TO KNOW WHY MY BUTTERCREAM CRACKED WHEN IT GETS DRY? NEVER HAPPEND TO ME BEFORE!!

Without knowingmore details it's very hard to say.
Most of the time there are two reasons:
1) the board you used under the cake was not stiff enough and caused the cake to flex when it was moved.
2) the recipe needs a bit more fat in it.