Without getting into the oddity that there is no gospel of “The Gospel”, I will just quote the places this appears in the Bible. When Scripture is used, it really needs references, at very least, you should have added some quotes so your additions did not look like they were part of the Scripture passage. This appears in the Gospel according to Matthew and Mark, chapter 27. The people who heard this were not specified.
45 From noon until three in the afternoon darkness came over all the land. 46 About three in the afternoon Jesus cried out in a loud voice,
“Eli, Eli, [
c]
lema sabachthani?” (which means “My God, my God, why have you forsaken me?”).[
d]
47 When
some of those standing there heard this, they said, “He’s calling Elijah.”
From Mark 15
At noon, darkness came over the whole land until three in the afternoon. 34 And at three in the afternoon Jesus cried out in a loud voice,
“Eloi, Eloi, lema sabachthani?” (which means “My God, my God, why have you forsaken me?”).[
b]
35 When
some of those standing near heard this, they said, “Listen, he’s calling Elijah.”
I will stand by my original supposition that it is possible that those who did not understand him were not the Jewish leader. I do not know. I wasn’t there and the Scriptures do not tell everything. Therefore, this is a possibility. If you assume too much, you add to Scripture. All we know is that some one, more than one, person nearby missed the point.