She always was. It's just that originally it showed how her plans never really worked out and she was just an immature child.
Bart usually came out on top although often at the cost of others. Lisa only really wins when no one else gives a shit.
Remember the save the fish episode where Burns takes Lisa's idea and turns it into a fish farm? Lisas all hippy dippy save the whales and Burns uses her to come out on top and become rich again.