Should I punish my players with a high CR encounter

[N'raac]

They are aware it was a direct result of their dilly-dallying, yes. I think that having the wizard throw back the fact that it was their fault the demon was released would be an excellent thing to throw back at them. I intend to hold that NPC in reserve, though, so that when he does make an appearance, later in the campaign, it will be especially vindicating.

I think the Wizard could make an excellent foil, as that "villain that blames all his own failings on the PC's" model. On the one hand, yeah, the demon was released due to a failure on the part of the PC's. On the other, it's not like the wizard was involved in any way in trying to prevent the demon's summoning. Once it was summoned, he ran while the PC's tried to mitigate their failures. The PC's are now working to send the demon back, while the wizard is doing...what, exactly? Nothing positive towards the situation, obviously. In seeking vengeance against the PC's for their failings, he may be impeding their efforts to send the demon back.

Lots of options, and you're in the best position to assess which approach fits best with the rest of the game, and the group. A villain whose claims have some justification, rather than "he's just evil", adds colour, especially when the main adversary is a "pure evil" type like the demon.

 

[concerro]

How can an NPC be incorrect? I do not understand.

They can have the wrong information.
As an example if an NPC says he was woman attack someone, but it was a man disguised as a woman.

With all that aside I am glad the session went well for you.