Nukes work better the more infra per city the enemy nation has, so it's especially effective for damaging whale nations. They also have a chance to destroy a power plant, which just exacerbates whatever damage was received, since you are now forced to rebuild enough infra and remove some improvements to get your city fully functional. Additionally, it's not likely a nuke can be stopped (rarely do people get VDS, because the chance for a successful block is so small it takes a very long time to pay off). Nukes start to lose a bit of its effectiveness, however, if you are nuking a nation who doesn't have high infra per city, since the damage caps at 90% of the infra.
Also, NB was mostly whales (which would have made them equally vulnerable to nukes themselves) and stockpiled a huge amount of nukes. Their net damage was significantly reduced because their nukes were getting spied on a daily basis. It's easier to just buy the nuke right before launching it so it has no chance of being spied off, unless they happen to be watching your nation with the espionage tab ready. That does limit how much you can launch a day, but it's steady and stable.
A setup like Fraggle's is a complete commitment to nuclear warfare, but her nation is constantly losing millions every day. While Fraggle can still continue to lob nukes even while she's bill-locked, without a steady supply of money she can't buy her nukes. If you're not Fraggle and you actually plan on buying back infra when you're done, you'll have to be prepared to have someone bail you out with a lot of money.