Old Model:
Five-star player enrolls and spends about four years at a school. There is a chance they play for the school and that they get drafted by an NFL team and earn large amounts of money. If they don't play, then they can transfer and sit out one year. This is a gamble given that the average player's ability peaks around the age of 27. Otherwise, they wait for another player to suffer and injury and hope to finally start. They receive housing, food, a small stipend, and a college degree.
The big takeaway, there is a chance that they are eventually drafted and earn a large income.
New Model:
Five-star player begins earning a large income by enrolling at a school. If they don't start, then they move to another school and earn a large income. There is still a chance that they eventually get drafted by an NFL team and earn large amounts of income, but the jumping from one school to another may reduce their chances of getting drafted by an NFL team. At a minimum, they receive housing, food, a college degree, and, with certainty, a large amount of income.
Here is a simple scenario to explain with numbers, omitting any discounting. When the player graduates from high school:
Expected earnings under the "Old Model," assuming there is a 50% chance of being drafted and the receive a contract providing them $4m per year, is $2m per year for the length of the contract, but they have a chance of receiving this income three to four years in the future.
Expected earning under the "New Model," assuming there is only a 30% chance of being drafted by an NFL team and receive a $2m per year contract and they also earn $1m per year in NIL money, is 4*$1m + 30%*$2m = $4m from NIL plus an expected NFL income of $0.6m per year. Earnings under the new model > earnings under the old model. In fact, it wouldn't surprise me if some players make the choice to remain in college to earn NIL money with certainty and not declare for the NFL draft due to the differential in expected income.
One more thing- under the old model, the players generated revenue for the school but most of the revenue remained with the school and could not be payed out to the players. The players received, housing, food, medical care, and a small stipend. The revenue generated by the starting players is greater than the benefits received. Where did this extra revenue go? I suspect a proportion if this extra revenue resulted larger contracts for coaches. I wouldn't be surprised if we see a decline in the rate of growth in coach compensation when the schools begin writing contracts and paying players.