If we look at its history, we see that he(kakashi) got it from an uchiha who awakened it just before he died and it only had 2 tomoes(i thnk). He worked on it and it matured to the maximum 3 of the regular sharingan and it was quite a strong eye as itachi praised it when he saw it. Up against the mangekyuo it was obviously no match and kakashi was caught in the tsukyomi genjutsu. Apparently, this encounter either affected the eye itself or kakashi killed off someone close to him because after the gap the eye becomes a mangekyuo with the jutsu kamuui which can warp stuff. This jutsu is interesting, and is it just me or does this ability seem to resemble the one tobi/ madara has? I think this means:
1.Obito and madara were related even if distantly
2.Madara's current eye is also a transplanted one and not his original eye, the idea being that a transplanted eye can't have the same power( sasuke's case is different because itachi had ms eyes) with ms as an original one.
i think da 2nd point is more likely and the eye madara took would have to be 2 or 3 tomoed and he developed its powers.
P.S: this is a theory and does not say who tobi is or is not.
P.P.S: just so you guys are'nt confused, the same power i said above means ametarasu, tsukyomi and susanoo