Yes the evil doctor strange took centuries to amass the power that he needed; but as soon as he had that power he went back to the exact time of the accident so that he could change that point in time. <--- The spirit of the ancient one appeared to the copy she made at a time I assume she believed he was powerful enough to either talk some sense into his counterpart, or be able to stop him in some way.
But yeah overall for me, this one didn't really make a lot of sense. Here you have both the time travel aspect, tohe amount of time it took for one version of strange to amass the power he did; and somehow the dead Ancient One; who in the Doctor Strange MCU film could never see past the point of her death, somehow able to return from the dead to send the 'good' Strange back In time to stop the evil Strange. Plus you have the universe this all takes place in seaming to compress itself down into what looks to be an infinity soul stone...

