It's not over your head, it just needs to be explained to you in the right way.

I'll try again, explaining in a slightly different way from how I first tried.
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*I'm going to stop using the term '2-cycle', and replace it with parity alg. I probably should've done this in the first place.
*1 swap = swapping 2 pieces with each other.
-A 3-cycle has 2 swaps (ie. for UF>UR>UL, the swaps are: UF-UR and UL-UF)
-A parity alg (such as y-perm) also has 2 swaps (
but instead of swapping one type of piece, there is 1 swap of corners and 1 swap of edges).
The total number of swaps needed to solve a cube will ALWAYS be even, this means a 3BLD solve can be deduced to 2 situations:
#1: odd edges and odd corner swaps. (parity)
#2: even edges and even corner swaps.
Imagine yourself in situation #2. Since 3-cycles are even (2 swaps), you can solve the cube with nothing but 3-cycles.
Now imagine yourself in situation #1. No matter how many 3-cycles you do, you won't be able to solve it, because 2 swaps won't ever add to give an odd number of swaps. Therefore you must apply a parity alg to perform 1 edge swap and 1 corner swap.
This provides a detailed explanation of why there will always be an even number of swaps.
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