The Great and Powerful Trixie was just a travelling showmare. Impress yokels with pretty lights, swindle them out of money, lather, rinse, repeat. Theatrical, cynical, bored as hell.
Sunset Shimmer was just a mercenary, a hired horn with a practically unflappable attitude and a barrage of offensive spells. Practical, cynical and bored as hell.
Twilight Sparkle was just a librarian on a train who happened to read about a legend in a book. Of a mysterious tree that would supposedly grant whoever found it their hearts' desire. Optimistic, reclusive and bored as hell.
One train crash. One bandit chief. One ill-timed show.
Is that all it takes for destiny to get on the rails?