I see that Putin's offer was a potential trap for Trump. No matter what Trump chose, he would be slammed by media and I think Putin knew this. If he refused right away, I am certain the critics would be screaming at the top of their lungs that Trump didn't want the Russian's questioned because he has something to hide.
Letting it play out that he considered it let the media establish the narrative that Trump is wrong to even consider it. They have closed the door on accusing Trump of trying to hide the collusion by not agreeing to let Mueller question Russians.
Yes, Putin set a trap. But it wasn’t a media based trap. It was a “why should I give you my guys when you won’t give me your guy”. Trump says yes, he’s weak. He says no, Putin says why should I send my guys to you. Trump looks weak again. The trap was all Putin on Trump. Media was just icing on the cake for him.