The bullet simply did not hit enough meat to reliably expand. Remember that you really don't want these sort of rounds to explode on skin or clothing contact. You want decent penetration in tough muscle and bone. Instead, you hit the ballistic equivalent of a bell pepper.
If you want something designed to expand fast on small game - pick a CCI minimag or Velocitor in Segmented hollow point or a 17hmr with fast expanding gummy tips.
The thing with small game is that their vitals are tiny. You gotta shoot really small to brain a raccoon, possum, squirrel, or rat. Think hitting a bottle cap. Get a solid heart shot and you wait 3-5 minutes for it to bleed out.