It's because there's a lot of casuals who enter League and MOBAs are one of the more aggressive playstyles-- it's not glamorous or exciting but you have to be aware of a lot of shit and while that might not translate as well on-screen when it is happening-- trust me, the disasters come about when it isn't and that's pretty wholly the difference. I've brought two casual gamers into League and one hardcore. The experiences were staggeringly different because the hardcore didn't need to be warned about skillshots, avoiding things, what was so bad about things, etc. because the logic was there-- Brand spells do extra damage after, Ezreal gets faster cooldowns on Q hits, Sona's auras activate on touch... the way roles are supposed to be (assassin vs support in playstyle). The way melee and ranged differ. The presence of CC in a fight. A hardcore gamer will understand certain things better than a casual, who does not process the logic like an experienced gamer might. The rest of League, after the logic, is knowing who can do what and when. Again-- an experienced gamer advances and learns far quicker. Ahri's damage is almost entirely directional and she has her ult to score positioning. Darius flourishes in a prolonged exposure to melee combat. There is a time and a place for defensive buys and defensive builds (and a difference). Spellblades work on champions who basic attack or create opportunities for it. Hybridizing can be important for teams with polarized damage. Knowing who can, and can't, could make or break a composition.
Convincing my experienced gamer to land Brand stuns while trying to convince a casual gamer to do so are very different things. The former realize that it must be a combo of E/W + Q, in that order, while the casual will be trying to fit this into dumping all their skills forward at once. Mana conservation is a skill the experienced gamer brings inherently and learns as they learn champions; the casual gamer may know the champ well enough, but might not understand in the same logic why mana conservation is important.
This isn't a bad thing and I'm not smearing casual gamers. They are welcome to enjoy video games at their own pace. It is worth noting that there is a difference and that they bring a certain play pattern to the game as opposed to players who learn more dynamically and understand the game's rulings a bit more inherently.
In this case, they learned a lesson in your case. Smite is an invaluable tool for junglers because it helps to push through the jungle and secure an advantage. It might not function as well in lane but hey-- lessons for another day.
We all screwed up and made basic mistakes. Not having a jungler with Smite just happened to be the flavour this time.
Casuals require the game in steps because they might miss the lesson, otherwise-- they might not understand that it was smite that turned the tables without the limitation in the first place.