with billions among billions of planets with different/unique compositions, properties its not really coincidence. its just math. with so many planets, with so many possibilities, even the unlikeliest of events can happen and shouldn't be a surprise. think if you have a big jar of marbles that have different colors all organized. the bottom 3 rows are only blue marbles, the middle 3 rows are all only red marbles, and the top 3 rows are only yellow marbles. imagine you shake that jar for 10 seconds. surely they will be scrambled. mathematically speaking, it is possible, yet very unlikely, that if you shake it for another 10 seconds, it will again be completely organized as it was originally. the math doesn't favor this to happen, but if you are given trillions of attempts, you could get lucky