Disclaimer: The Lion King is a fictional movie (duh). I know what fiction is. PLEASE DO NOT EXPLAIN FICTION TO ME!!! This is called ruining the Lion King, (based on reality) K, thanks. Let's go!
1. "King of the jungle" status does not pass from father to son.
Being a male lion is more like being in the movie Highlander---there can be only one. A pride is made up of a bunch of female lions and a few male cubs, but older male lions wouldn't be tolerated much. When male cubs mature, they are tasked with leaving the homestead to find and create a Pride of their own. Lion territories are quite large—15 square miles on the low end, ranging up to nearly 400—and are passed down through generations of females.
2. Simba and Nala were definitely related!
Disney conveniently forgot to put that little disclaimer on the film. Ewww, but it's true. A female lion in a pride will only ever be allowed to have cubs sired from the pride male...and there is only one. Any pre-existing cubs are generally killed off by the new pride male because his pride and progeny are exclusively his and any other male cubs are considered a direct threat to his sire line. All the females in a pride would be related---sisters, cousins, aunts, etc, so Nala being one of those cubs would mean both she and Simba had a blood relative in one of the lionesses.
3. Lions are not monogamous
Lions basically mate with all mature females in their pride in order to ensure their sire line continues. Pride lions have actually been known to kill female lions who refuse to mate with them. There is also a benefit to the lion familial structure, because lionesses do most of the hunting for the Pride, so in order to ensure a healthy Pride and food for all especially in meager times, it is beneficial to have many lionesses vs just the one.
4. Lions don't eat grubs/bugs and neither do warthogs
Even in desperate times, lions do not eat grubs and bugs. In order for an adult Lion like Simba to maintain his constitution, he would have to eat the equivalent of 6 bugs a minute in order to survive. If there isn't a meat food source, they will move and look elsewhere until they find one instead of live somewhere were none is available. Warthogs are grass eaters who do not typically eat bugs. Meerkats however, would definitely find insects appetizing.
5. Time does not erase instinct
There is a scene in the movie where the unassuming Nala ends up hunting Pumba because that is what a lioness would do and is only stopped by Simba who lets her know they are "friends." (Cue the laughter). Even lions fully raised in captivity and hand fed, which Simba was never, still slip into their instinct when there is a threat near, food, or someone or something unfamiliar to them approaches. This is why zoo handlers have been mauled to death. There is no world where Pumba and Simba and Timone would be friends because they are predators and prey.
6. Lionesses aren't sticking around for nothing
A pride lion becomes so because he can defend the Pride against invaders, other male lions, and of course the whole procreation thing, but given how run down the land was and lack of food under Scar's rule, there would be zero benefit to them staying with him and they would have left. Lionesses need food and energy in order to hunt and nurse their young and despite the visual of what appeared to be hundreds of Hyenas on the Pridelands keeping things in tow, having a pack of 100 hyenas as well as lions all vying for the same food source would not happen as none would allow it too. You want to have a pride or a pack with numbers, but too many and that's just a detriment to themselves by having too many mouths to feed. I mean what is there to protect against, if you've killed off everything on the land, let alone, to have anything left to eat.
7. There is only one place where animals all gather
...and it's not Pride Rock. Because of the real and eminent danger of being eaten, predator and prey would never gather together for any long sustained period of time, let alone to honor the birth of a baby cub, who will then grow to be a lion who will probably try and kill and eat them. The only place animals "gather" is a watering hole because all must drink in order to survive but it is often the most dangerous times for the animals because not only are there alligators lurking beneath the surface ready to kill, but other apex predators surface side who are just as hungry. Everyone has an eye out and it's a do or die situation vs. a fun celebration.
8. Male lions are not teachers
Mufasa is given a lot of due as almost the sole guide to Simba being raised to hunt and how to be a lion...the major problem with that is female lions are the ones who teach cubs to hunt. Male lions spend A LOT of their day actually sleeping and it would be counterintuitive to train up a cub to take their place. They aren't in the habit of sharing status with competitors to their throne.