Practice Makes A Man Perfect
It seems like icing is not something a non-specialist can do without practice. You need extreme patience, dedication, and stiffness in your hand to achieve your ultimate goal. Experience is another crucial ingredient. Applying it before the cake cools down can melt it really soon.
You need to make sure the cakes are cold if you want the icing to maintain its shape. That’s presumably not what this person did, which is why their cupcakes look like a mess. The white icing is nowhere near as clean and refined as it should be, rendering these desserts a failure.