Ulf was treated like royalty because he very well would be and these men would want him to remember their faces so they went out of their way to help him out.
The bodies in the cell had been disposed and due to how it was disposed, no one questioned if the prisoners escaped or not nor did they bother looking for the ones that did so.
They were probably having fun so no one thought anything of it as they were forgettable.
Ulf noticed that no complaints were coming from the cells but he was also certain that he had left them alive so if there were no complaints then that could only mean they had found a way to use the situation to their advantage.
Ulf knew the first thing they needed to do was make sure that Skarde was alright, Ulf knew he wouldn't be enough to rally the people around him as he was imprisoned by Ragnar.
The men would be skeptical to follow someone even his brother didn't trust so Skarde was the key to mount a counterattack.