My assumption -- with the initial infection the body creates antibodies to fight off that original strain. As it spreads to more and more cells and churns out c

My assumption -- with the initial infection the body creates antibodies to fight off that original strain. As it spreads to more and more cells and churns out copies, it mutates slightly every time it replicates. And then each of those instances replicates and mutates a little more, becoming a bunch of different strains. And while initially the original antibodies will be effective to start with those strains, eventually they'll muttate enough to where you have so many different strains where suddenly the antibodies aren't working anymore and that's probably the point where the immune systems gets overloaded trying to produce antibodies for all these different strains, and as soon as it catches up it all becomes worthless, because in the meantime a ton of other different strains have mutated in the meantime, and so on and so on. tl;dr snowball effect