Lions fight for the territory and for their dominance.
In this space of action if it is injured it will die.
First of all it is very unlikely to be a one on one fight. Nearly all prides have at least two males running them, some have 3 males. It depends on the size of the territory and the numbers of females.
Most takeovers are gradual. It will start with roaring their presence on the fringes of the territory and then gradually easing their way further in. The first showdown is usually just each ‘team’ judging how strong the opposition is. The usurpers will almost always retreat.
It is interesting to watch the reaction of the females at this time. Those with cubs tend to retreat towards the other end of the territory knowing the outcome if new males take over but those without cubs tend to be very shrewd judges as to who is going to be victorious and have been observed encouraging a takeover.
Those taking over will try and isolate the 2 pride males. If they can drive one of them off or gang up to overpower that one male then the pride becomes very vulnerable and the males taking over will then have an easy time with the takeover. I will not go into the grisly details of what happens to the cubs as we all know that. Fights to the death do happen but are relatively rare. It makes good television of course which is why it is so prevalent in wild life documentaries. Should the pride males stick together and defend together they stand a much better chance?
The 2 ousted males, depending on what state they are in may try to take the pride back but if all the cubs have already been killed them will tend to move on. Sometimes they form alliances with other males and may even take other prides over but if not will eventually die usually at the hands of the local hyena clan.
As for cannibalizing dead bodies, yes, though sometimes members of the pride do refrain from joining in.