Robinson crabapple is generally a great tree for this region, and it looks like you have taken great care of yours. But, as you mentioned, the weather recently has been very tough on trees around here. Crabapples are prone to sunscald, where sudden extreme temperature changes cause the bark to crack open. Last November we had a very big, sudden temperature change - after weeks of warm weather, the temperatures plunged before the trees were hardened off and prepared for winter. Many people have reported a lot of damage from this weather event. After the bark cracks, there is not much you can do, just take normal good care of the tree, and hope it survives. The current recommended is NOT to wrap or cover or paint tree injuries, as this promotes insect and diseases.  It is possible that the snow and cold this spring caused some damage to the leaf buds on your tree, causing it to look a bit punt right now; but it should recover well from one defoliation event.  If unfortunately you have to plant a new tree, be sure to wrap the trunk over winter with crepe tree wraps, available at most hardware stores. Wrap in the fall, and remove the wrap in spring; do this for 2 or three years, to prevent sunscald until the tree is old enough to grow thicker bark.

Here are some links to CSU information about sunscald and crabapples.

Flowering crabapples fact sheet.  http://extension.colostate.edu/topic-areas/yard-garden/flowering-crabapple-trees-7-424/

Which crabapple varieties are best? http://www.colostate.edu/Dept/CoopExt/4dmg/VegFruit/Fruits/crabaple.htm

Winter weather brings sunscald. http://www.colostate.edu/Dept/CoopExt/4dmg/Trees/sunscald.htm

Good luck, growing trees in eastern Colorado is always a challenge!