Slight tangent: how "new" is this phenomenon? I don't remember character optimization being an issue when I was playing D&D in the 80s and 90s. The first time I heard someone refer to another character as "a munchkin" or a "min/maxer" was in the early 2000s with 3rd Edition. Now it's fairly common, even expected, in some groups.
The phenomenon is ancient. We had it happening in the early and mid 1990s, and I heard tales of it happening in the 1980s.
The difference now - indeed any time after about 2000 with D&D - is that instead of figuring it out for yourself, you can just get on the internet and find a build that someone else came up with, and which is often way more broken than even a serious munchkin could have before.
I have a player who is a "recovered munchkin" by his own admission. He didn't start that way, but he quickly got into optimization, couldn't stop, became a bit of game-ruiner aged 13-17, then as he got a bit older he realized how bad he'd got and stopped. He still likes to make powerful characters but now makes it fun for everyone, not just him, and doesn't go as far. He does love to message me ridiculous builds he find though.
EDIT - The stuff he figured out by himself was a joke compared to 3.XE-era internet stuff. Like in 2E he realized you could completely legally have a Dwarf Fighter/Speciality Priest of Clangeddin with a kit and weapon specialization, despite Speciality Priests, Kits, and Weapon Specialization all being theoretically forbidden from multiclassing - he just found very specific and clear exceptions for all three cases. He later further enhanced the character with Combat & Tactics stuff, most of which he could only access because he had weapon spec. None of this remotely "broke the game" of course. He seemed powerful but him at 10/10 next to a 9th-level Mage, who has more impact on the course of most adventures? The Mage by miles.
Rifts and Shadowrun were total bait to this guy of course, but his worst behaviour and when we did have real issues was entirely in Cyberpunk 2020, where he played a ridiculous Solo who burned 8 EMP down to like some tiny amount of Humanity and just killed everyone and everything with dual-wielded .50 Desert Eagles, electrothermally-enhanced, spitting some kind of silly ammo, with special implants (all fairly cheap and legal from early Chromebooks and Solo of Fortune, though I think ETE enhancement was CB3) so he could independently target his pistols/cyberarms with no penalty. Obvious armoured head-to-toe in subdermal armour, eye-visor, bulletproof trenchcoat etc, carefully maximizing the layering rules. That might not have been so bad except the player actively tried to turn every situation into a running gun battle, no matter what the rest of the group wanted to do, or what plan he'd actively agreed to.
He is of course an extremely successful lawyer in his real job now...