This is all just a split second look at the future from obito as the rocks about to fall on kakashi and he's seeing what his life and the world will be like when he's gone. Then at the end of the series we get a flashback with obito letting the rock crush kakashi and leaving the cave with rin. Then in the epilogue we see 1-2 year time passing with minato as hokage, kushina's alive an narutos not a jinchuriki. Then we later see obito as hokage and rin as his wife.
I think it would be cool because none of this would've happened if obito would've just let kakashi get crushed. That was literally the turning point in the manga for everybody.