How did this evolution happen? Easy: you load a cart; so the cart takes on the burden; just as you, by accepting responsibility, are taking on a burden, too. In other words, any action you might need to be responsible for achieving is just like the annoying junk in your trunk, holding down the car!
From the same Latin root, we get the English, caricature. You can see the c-r root in both. The word for “cart” turned into caricature because, well, a caricature is an overloading (!). A caricature, then, is literally just piling on more and more needless extra, exaggerated observations into the picture you paint, until your trunk is similarly burdened down!
Funny how, in English, over-loading a car is an exaggeration, a caricature. But in Spanish, it is just the normal way of taking responsibility.