It’s not well understood how the Tarot works. Every reader has their own theory. CG Jung thought that all divination methods, including the tarot, worked through sincronicity. That is, that there is meaning behind the events that occur. The tarot acts as a microcosim for your life, the meanings in the cards reflect the events and the greater meaning behind those events.
The human mind has an incredible ability to find meaning, it searches to create meaning in everyday events. My feeling, from using the cards, is that they allow the mind to tap into its ability to search for and create meaning. The mind, linking the left (rational) and right (intuitive/creative), taps into the unconscious to find meaning in a reading. The story that evolves, really comes from our own inner wisdom. I do not think the cards are ordered by a “higher power” but rather by our ability to find patterns and make meaning.
The idea that the meaning in a reading comes from within us is the reason why I typically don’t use the cards for fortune telling. I rather use them to tap into my inner understanding of a situation to reveal the knowledge that I already possess. The images allow me to step aside from the rational and access the hidden. It is when I put aside the rational that I’m able to know what to do and able to see the (consciously) unknown.