only the one who used the weapon at the end, so button pusher only, the aiming person only helped button pusher adjust the weapon the person giving the order is comparable to the npc who tells the player to do the 'quest' to kill 'enemies' .
in games, xp comes for the final killing shot, I think. In that sense, the one who pushes the button gets the xp provided they have the autonomy to defy orders.
The nuke designer gets int xp The builder gets tech xp The launcher/aim gets dex xp The order giver gets bullshiet xp.
Before we can choose, I think it's important to determine which of the choices is still alive after the nuke was detonated.
i like to think this further. What if you're a everyday worker in a ... let's say steel factory, and out of nowhere you get xp. What would you think? And would you get still xp if you're making the tools to create a weapon(specialized tools and general tools)?
All involved In launching it would. That said, its probably against heavenly Dao and they all get smited by heavenly lightning.
On the other hand it can be like pokemon and thus everyone who participated in the fight somehow gets a fraction of exp with a bigger chunk going to the guy who last hit, aka, button pusher
The real answer is that it depends on how gamebreaking it is. If nukes aren't gamebreaking, then... If they're not in a party, EXP is shared according to contribution. The person who aimed and the person who pushed the button get the EXP. The person who gave the order gets nothing, since he didn't do jack. When was the last time a quest giver got EXP for sending you to kill something? Otherwise that guy in the beginner village who sends you to collect 500 smoked wolf testicles would be the strongest man in the kingdom. If they are in a party, they all share the EXP. If nukes ARE gamebreaking, all three participants get zero EXP. The excuse could be something like how they're too far away. For example, if you're farming and your party member leaves the map, they won't get the EXP from your kills anymore. Otherwise the prince could join a party and be levelling while his team of elite knights are out grinding for him (wait, that's not a bad idea... but let's ignore it for now). That nuke is far, far, far away. If the three participants were close enough to get the EXP the explosion / shockwave / radiation would cancel their life subscription.
The explanation for not getting xp might also be that somebody made a nuke, someone armed it, and someone fired it, but outside of skill progress on the first two, there is no gain. Outside of a literal system attachment, none of them got squat from such a form of mass killing be it in personal power or ability to fight generally and now they are out of a nuke provided they don't have resources, the setup and ability to make and fire a new nuke. It would be like using a consumable, do you get xp for chugging an elixir for maximum healing? But you can approach this question lots of ways, and there might easily not be an exp mechanic in game or tied to the nuke at all.
It's a game world, creating nuke would probably be created by a group of 20 people, they have the minerals in their inventories and the items needed to create it and launched it.