Titus was a confident man, a powerful warrior, and a commander in his own right. He was deeply fixated on keeping the situation under control.
The Brass Cauldron was the cause of this Daemon invasion. He had to keep it in his own hands and absolutely could not surrender it to anyone else, even if that meant falling out with Li Qinwu!
It was not that Titus was being unreasonable. He had simply been burned too badly before, in both Space Marine 1 and Space Marine 2.
In Space Marine 1, Titus had been deceived by a Daemon-possessed Inquisitor, who claimed that putting an unknown artifact-which was actually a Daemon Artifact-into a launcher and firing it would resolve the planet's Greenskin crisis.
Instead, the Daemon Artifact was successfully launched, tore open the veil of the Warp, and summoned a Daemon Prince into realspace. Titus had needed several punches to beat the Daemon Prince to death. It had been a real pain.
Then, in Space Marine 2, the same thing happened again. This time, however, a Tech-Priest was the one who got duped. He launched something or other, thinking it would resolve the planet's situation, only to summon a Greater Daemon of Tzeentch just like that. Titus had gone to enormous lengths to hack that Greater Daemon of Tzeentch to death.
Twice was enough. Titus absolutely could not let himself get tricked a third time. Wouldn't that make him a complete dumbass?
So, even at the risk of falling out with Li Qinwu, he had to keep the Daemon Artifact in his own hands, then hand it over to someone he trusted to deal with.
Yellow Sand and Swift Shadow knew that the Brass Cauldron was vital to Li Qinwu's future. They had to keep it under their control!
Titus's attitude