After visiting with a relative's husband lately whose an assistant Pro Football Scout. I was very blessed to understand how the NFL recruits lately for personal qualities before encouraging a player to declare.
There are criteria when facing a decision to draft or not a player, from a signed not drafted player recruiting. The negatives are playing for one college team but decide to transfer to another team, other variables as a team player, getting along with coaches and teammates are a big plus.
The transfer portal has become that seductive element in the NCAA that shows the NFL that if a player does really well, contract issues would erupt in demand for more than the current contract. With the NFL salary cap, teams have a tendency to shy away from NCAA players willing to transfer out as currently active with the team.
Players the NFL seek are examples as in Shakir of Boise State and Allen from Wyoming. both on the same team drafted. He said many transfer players that do sign up wind up on the development squad or injury reserve to test their willingness as a long term contract.
My hope is, the NCAA will go back to a one year pause for any and all transfers, but the NCAA has not bothered to tweak the transfer rules.