Eren didn't forget to place a visual capture artefact that'd record the whole event in a 3D spectral format. It wasn't that he only wanted to look at his revenge-fulfilment trophy. It was only a part of the reason.
Eren was going to make multiple copies of the recording and sell them to the rest of the audience who couldn't participate in the event. He had already announced that the buyers would get to buy the recordings at a reasonable fixed price this time, sans the bidding format.
This wasn't because Eren was satisfied with the amount of Extols he made. Scrooge felt all the money he had collected so far was still not as much as he would like to be under his control.
However, he had another reason for spreading the visual content of this act. He wanted to sully the Slughorn name and damage its reputation. And what better way to do it than sell it to the degenerate rankers who would spread the captured content like an unstoppable wildfire.
