Smartbomb fleets are a very high risk/high payout fleet type. If the ships are not placed exactly where the enemy fleet is landing, the short range of the smartbombs means that very little damage is applied and the fleet will likely get welped. If it works, however, hilarity ensues. The way it generally works is the enemy fleet cynoes in the SB fleet exactly where the other fleet is warping to, generally in an intercepting bubble. This leaves the enemy fleet precious seconds where they take the full damage of the smartbombs before they can warp off. Realistically, anything that warps in directly into the smartbombs dies instantly before being able to warp again.
In this case, Nulli Secunda had been fighting an HBC fleet comprised of Rokhs with Nagas (generally a difficult fight at best). Dani Eli and Unite's FC ships were both destroyed and podded, and after losing a number of Nagas without causing much damage, the Nulli fleet wisely decided to bug out. The HBC decided to not follow the fleet, and found out a few minutes later that the fleet had dissappeared.
The reason for the disappearance: Rooks and Kings had gotten into the mix and managed to surprise the Nulli fleet with a Typhoon/Geddon smartbombing fleet. RnK executed the operation perfectly, cynoing the fleet on a drag bubble just as the Naga fleet warped. The result was a hilariously effective smartbomb run... In total, 55 Nulli Secunda ships were lost, essentially the whole fleet (and pods).
After seeing a few attempts at smartbombing fleets in the last couple of months, specifically on the Northern front, RnK finally managed to remind everyone how effective they can be when run successfully.