Are not the disbelievers mentioned in the verse (And they will say, "Why do we not see men whom we used to count among the wicked?") those who realized the error of their methodology in the grave after witnessing the torment of the grave?

The disbelievers mentioned in the verse: ﴿And they will say, "Why do we not see men whom we used to count among the evil ones? Did we take them in mockery, or have our eyes failed to perceive them?"﴾ said this out of regret and sorrow for their fate, and in self-reproach. Their saying, "whom we used to count among the evil ones" refers to their perception in this world, and this is a rhetorical question of reproach and astonishment. Commentators have interpreted this question as expressing regret for their situation in Hell, in contrast to the salvation of those whom they mocked.

As for the states and terrors of the graves, there is no detailed knowledge regarding them, nor do the texts indicate that the inhabitants of the graves (whether righteous or wicked) know the state or fate of others. Rather, they are concerned with their own affairs and what they will be questioned about. The terrors of the Resurrection are immense, and only Allah knows their full extent. They cause a person to forget everything. How then could a disbeliever know the fates of the believers before he himself is in Hell?

There is no problem with the inhabitants of Hell asking about the fate of the believers and their salvation from Hell, whether the question is literal or intended to express remorse and self-reproach.