This is from an article an article in LV Sun and I think it paints a pretty fair picture of what is most likely to have happened:
Sluka's current agent, Marcus Cromartie of Equity Sports, said Sluka was promised $100,000 by a UNLV assistant coach.
Multiple sources said no contract was ever signed, though all NIL agreements are supposed to go through official clearinghouses. UNLV’s NIL collective uses Blueprint Sports to handle its contracts.
Cromartie said that because Sluka was still completing his degree at Holy Cross, he could not sign a NIL contract, typically done with booster-backed third parties called collectives that serve a school's athletes — until after he enrolled at UNLV later in the year.
Sluka did not join the team until preseason practice in August. No written contract was ever put in place, Cromartie said.
“In July, there was no NIL payments. There was no $100,000, I guess you could say zero dollars. He was given a $3,000 relocation fee and that was it,” said Cromartie, who declined to identify the assistant coach and said UNLV head coach Barry Odom was not involved in the initial discussions.
Cromartie said after several weeks went by he reached out to first representatives of UNLV's collective and then Odom to discuss ways to pay Sluka the $100,000 he said the player was promised.
Cromartie said he suggested payments of $10,000 a month over the next five months and even $5,000 per month and was declined. Cromartie said Sluka was offered $3,000 per month by Odom.
“At that point I think Matt felt lied to. At that point he just wanted to stand up for himself,” Cromartie said.
According to a statement released by UNLV athletics on Wednesday, the program considered Sluka’s demands to be “implied threats” and a violation of NCAA rules, and declined to pay.
“Matthew Sluka’s representative made financial demands upon the university and its NIL collective in order to continue playing,” the statement read. “UNLV athletics interpreted these demands as a violation of NCAA pay-for-play rules, as well as Nevada state law. UNLV does not engage in such activity, nor does it respond to implied threats.”
When he was informed that no money would be forthcoming, Sluka followed through on leaving the team.