Why are TOP LANERS mostly 1-2 levels above everyone else??!!??! I DUN UNDERSTAND...!

so shouldn't the top laner be equal to adc in exp

Nope, because you're forgetting about someone: the Support. XP is shared to all nearby teammates, the Support and ADC are sharing the XP, so neither is as high a level.

Mid and Top are usually neck and neck for level, since they're in the lane Solo.

solo lanes get solo exp so usually mid is also a level ahead

Usually top laners farm and focus on their own lane, since they can't roam very well. Mid lane roams cause rift herald and dragon, bot lane has split exp between support and adc, and jungler is always ganking

WAIT WHATTTTT! EXP in proximity is shared by champs... my whole life is a lie!

After laning phase is over, bot is usually mid, the mage is also usually mid, top laner usually rotates between solo pushing the stacking sidewaves in the top lane/ mid, thus getting all the exp to himself.

You sir, need to read about the in-game mechanics.

For example, a solo lane will get to level 2 after killing the first minion from the second wave, whereas botlane will take longer (it takes the full second wave, I think).

thnx everyone

Sometimes as jungler I unintentionally leech exp from mid lane too just by being close by like doing raptors in their pit while waves are pushed to towers, or if scuttle gets pushed near the mid river bush, or just crossing jungle quadrants. This never happens top lane with no jungle camps close by the waves so for the most part top lane gets all solo exp