It's what goes on in the mind that's hard.
Obi-Wan has trusted Maul a great deal for quite a good number of years, now. Of course, this is only in the sense that he trusts Maul to always walk the path of the dark side. It was never in doubt. Where they stood has been a solid place for so long that Obi-Wan now has no idea what to do with this Maul who has broken the cycle. Well, somewhat broken the cycle.
The Force offered little insight on Maul's decision, and Obi-Wan doesn't know what to make of him anymore.
Certainly, Obi-Wan can't trust him like before. Where used to lay the safe confidence that Maul's intentions were deeply twisted by violence, now stands the possibility of something else. An endless stream of questions without answers piled themselves up; Would Maul truly be satisfied with only the death of the Emperor? Could he be intending to kill Luke, to take away my hope for a better galaxy? Does he think he can catch me off-guard?
None of it seemed to add up.
Regardless, Obi-Wan decided that he'd better keep an eye on Maul.
As the twin suns rose, Obi-Wan insisted that Maul return with him to his home. Better there than Maul being unsupervised in the vicinity of the chosen one. He didn't expect Maul to agree, but he did. In fact, Maul agreed immediately and without any fuss. It was unnerving and quiet. The way back was equally so, and when they got to Obi-Wan's home and he presented a place for Maul to rest, there was no response received.
Maul was sat on the cot he was provided, blankly staring at nothing. This wasn't meditating - it was something similar, and far less healthy.
Hesitantly, Obi-Wan reached out the smallest bit with the Force, to feel for Maul's presence. It was a lot more muted than it had been a few hours ago, but he could sense also that Maul was a lot more vulnerable now. A lot less defenses, though the few that were up held stronger than ever before.
Plenty attempts at actual conversation had failed, and this situation was too risky and the stakes too high for him to simply leave Maul to his devices without knowing why he shut down. Testing his luck, Obi-Wan pushed further through Maul's mind.
Most things were off-limits. Even in this odd state, Maul's mind was clearly awake and aware of what was happening, and Obi-Wan quickly surmises he'd be unable to pry anything from him if it wasn't willingly given. The only thing he could gleam from his mind was his emotional state, which was projected and easily communicated. It was a highly unpleasant sensation, all too familiar, in fact.
Obi-Wan did not want to know anymore. Letting go of the connection, he staggered slightly at the emotional whiplash. His hands shook, his breath unsteady. Since he was a child, Obi-Wan had been taught to make peace with the universe and his inability to fight against it meaningfully when things were unfair. It took a long time for the message to get to him, so long in fact, that he sometimes wondered if his struggles with this might've played a part in Anakin's fate. Decidedly, he could not wonder for long without forgetting the lesson.
It was clear that Maul never received such a lesson. Maul had been taught to use his anger at injustices as a weapon to use against anything and anyone in the way, which couldn't lead to any good coping mechanisms for all he'd been through. The feelings that Obi-Wan sensed from Maul had been deeply hopeless. It was impossible for Maul to exact revenge upon the Emperor, and that fact robbed him of all the meaning he'd ever been given.
"Maul."
...
No response.
Time for a different approach, then. Obi-Wan grabbed his comlink before walking back over to Maul, handing it over. "Isn't it high time you contacted your 'apprentice' and informed him that you decided not to kill me this time? I'm sure he would be quite relieved to hear from you about it, after he left in such a state."
Finally, Maul grunted quietly in acknowledgement, seeming to come back into his body as he blinked at the comlink in his hands. Of course, his apprentice. It would take time to get his trust back after what he pulled to get here, but he could do it. If nothing else, Maul knows he can at least out-manipulate most people.
With that, Obi-Wan nodded and politely sat across the room to give him space without leaving him alone to make the call.