According to the Internet culture database 'Know Your Meme', the challenge started to take off in 2019, largely on Facebook, Instagram, and Twitter. At its core, this 'before and after' challenge is a wholesome, socially acceptable way to brag about how hot you used to be, how well you matured, or how hot you were, and how well you matured.
Call it narcissistic, but I think self-love is important. We tend to be too hard on ourselves; we do it because we want to excel and be the best version of ourselves, all the time. However, this entails a lot of self-criticisms, and that inner voice that constantly tells us how we could've done things better can really hold us down. If the 10 Year challenge with its cool pictures silences it for some of us, so be it.
