It was precisely because he had realized this that Adam reflected on himself this time.
As he had said, it was his fault for failing to give the four of them enough security, enough for them to subconsciously be willing to trust him.
When he had returned last time and seen that both the Hanging Gardens and the Human Alliance were on the right track, he really should not have turned time back to the day after he left.
That had indeed ensured that, in the four of their perceptions, it was as though he had never left. Yet precisely because of that, their subconscious minds could genuinely believe that perhaps the possibility that he had never left did exist.
Subjectively, they knew Adam had left once, then rewound time to the day after he left, and they believed it had to be true. But objectively, they had no memories of experiencing Adam's departure, so that understanding was not stable enough.
Besides that, the records about him in countries outside the Human Alliance would not state that he had returned after leaving this world for several decades.
If he had not turned back time then, or even if he had not rewound it so thoroughly, Adam's departure this time would no longer have been the first time he had vanished without warning for centuries. There would at least have been a precedent of him disappearing for several decades.
In that case, there would certainly still have been ambitious people trying to challenge the Human Alliance, but the scale would never have been as enormous as it was in this history, to the point that doubt had arisen in all four of their hearts.
That was also why, this time, Adam had handed the choice of whether to turn back time