yeah they went to great lengths to stop most multiclassing its usually limited to quick 3 levels or less on most builds.
i also want to point out another option in the damage parsing to put a wrinkle in it.
try it with a rogue that has say a +1 shortsword with 1d10 poison damage on it, or a fighter with 2 warhammers and thunder damage. its going to take those neat numbers and blow them to smithereens. as even if the monk has a like enchanted weapon they only get the bonus damage dice on their first attack as "all the extra attacks" are "Martial arts" attacks. if you dual wield on the monk attacking with the offhand weapon it is a bonus action not allowing you to flurry or martial arts or stunning fist etc.
There is also the fact that if you scale up to lvl 20 all the "weapon wielding" classes can obtain +5 weapons aka +5 to hit, so monk literally loses 25% chance to hit on all their subsequent extra attacks and they need to spend ki to have the same attacks as a fighter the fighter with drastically higher hp and ac will gain bonus to hit and extra damage dice on every hit with a good magic weapon literally every weapon wielding class with extra attacks can dumpster monk for damage due to this even healers like the warpriest.
I just didn't want to start with the uppercut.
This is why monks literally either need handwraps to be enchantable and bridge the gap, or their class abilities need to be better and more interactable to "steal more" from other classes. at every level range with nothing being done about monk hp or ac monk should at minimum always parse higher than fighter for damage as a minimum "quality of life". they need an especial amount of love in long ranged combat .... flurry really needs to interact with their ranged weapons.
Honestly probably both.
