I've been playing Minecraft for a while now and I've had a few random experiences with the game while I'm exploring a cave to just spawn 50 (obviously exaggerated) mobs on my character for no resone at all like the the recent example I collected 24 diamonds 11 golden apples diamond hose armor 2 stakes of iron 5 ender pearls and a stake of lapis then while I'm in a chest in a mine cart the game spawns no joke 4 zombies 1 zombie villager 3 baby zombies 1 skeleton and 1 creeper like wtf of Corse I died and I was so deep in the caves I don't think ill find my stuff
This is normal, especially if you didn't light up the area well, or worse, didn't even use any lighting since you can easily see in the "dark" (IMO, Mojang needs to make it so dark caves are pitch black, no matter what the brightness/monitor settings are, then nobody would ever go caving without light sources). However, lighting up caves can concentrate mobs in the remaining dark areas, increasing the chances of encountering multiple mobs at once (in general, the number of mobs I encounter increases as I explore more of a single large cave system, easily doubling or more until nearly all of it has been lit up; the most extreme sessions have occurred when exploring a cave system surrounded by previously explored areas).
Also, zombies in particular have a large "follow range" so they can track you down from far away; in fact, prior to 1.8 it was up to 100 blocks; I regularly encounter massive zombie hordes while caving (they are rarely a threat though since I am well-prepared, e.g. Protection IV armor, Sharpness V sword, Power V bow, all that; I actually don't go caving at all until the "end-game, when I have my "caving gear" made - branch-mining is vastly safer and faster at gathering diamonds and other rare resources).
Here are some examples of what I've encountered while caving; the much larger caves in my mods further increase the threat of mob hordes since they prefer to spawn in flat, open areas and they have a clear line of sight (I also reduced the "no spawn" zone from 24 to 16 blocks so they spawn closer to the player, either way, zombies can target you from further away, which also means that after a while their numbers will decrease as other mobs fill up the cap):
You can tell that there were way more mobs than shown here from the XP orbs everywhere
This is a zoomed-in screenshot from the same ravine shown above:
This gives you an idea of how many mobs I regularly encounter, an average of 365 mobs killed per play session; nearly all were killed while caving (I do not use mob farms and only farm animals for a short time at the start of a new world); the average per play session spent caving is even higher (around 388 vs 125; I spent 222 sessions caving); and yes, the number of deaths is correct - I've never died in this world (the last time I died at all was well over a year ago):
This has almost no impact compared to the "call for help mechanic", which affects all difficulties, since the chance is on average only 5% (0-10%) per hit, while zombies call for help with every hit they take (both excluding the killing blow, so if you kill them in 2 hits there will only be a 5% chance of a reinforcement, but 100% chance of all nearby zombies becoming aggroed towards you). Even with the increased chance (10%) that I gave them it is hard to observe the effect until a zombie spawns within sight (they can spawn within 7 blocks of the zombie that was attacked), otherwise, they may spawn in a nearby cave with no path to you (not necessarily disconnected but they won't pathfind unless they can find a connection within their follow range).