They did succeed, to a certain degree, and were on their way with Master Even Piell and his men. Not to mention, as Anakin tells Ahsoka, the prison is meant to harbor and kill Jedi, so it’s particularly lethal to the strongest people on the mission.

It was wildly risky because they all had to freeze in carbonite to escape the lifeform detectors on entry, and it wasn’t a guarantee that would work. In addition to Obi-Wan Kenobi, Anakin Skywalker, and Ahsoka Tano (who wasn’t supposed to be on the mission in the first place), troopers Echo, Fives, and the rest of the 501st Legion went along. He had hyperdrive coordinates that were harmful to both sides, and the Jedi needed to save him from being killed or from those coordinates from getting to the enemy. In Season 3, Episodes 18 through 20 - “The Citadel,” “Counter Attack,” and “Citadel Rescue” - a team of Jedi and Clone troopers head to the Citadel, an impenetrable prison where Master Even Piell was being held. Clone trooper Echo’s helmet during the battle at the Citadel in Season 3 of ‘The Clone Wars’ | Lucasfilm Clone trooper Echo was presumed dead after the Citadel mission in Season 3

Star wars echo and fives