There were witnesses, Jesus said" One of you will betray me" - that makes 12 witnesses.
Then Judas came with the Roman soldiers - agains witnesses.
The NT was told and later written down by Jews, living, thinking in a Jewish tradition and culture.
Saying this is all was made up means you think the Jews in those days made up a story about Jesus. The people were not Christians at that time , but Jewsish.
To deney the historical people of those days is saying the Jews were lieing and that is rather anti semetic.
We do not have statements from all the alleged witnesses. All we have is some writing in the New Testament. Moreover, there was no written history covering that period, much less something provable regarding the alleged Judas and his alleged actions. I don't think anyone knows details about the alleged witneeses, especially what their beliefs were with respect to religion.