Transfer Portal 2024 I think it gives staff time to meet to identify positions of weakness, and build a plan for what they want to go after in the portal or via HS recruiting. Then they also will do year end meetings with each player to talk about how the season went and what the outlook is for them. The coach may tell them that they are looking in the portal for other players at their position and they may end up in a position battle or buried on the depth chart. If a team then takes someone from the portal and a player ends up 4 or 5 on the depth chart they still have a time to decide if they want to get in the portal.
My guess is that guys who hop in the portal early are either studs that are unhappy with their current situation/had a coach leave etc or a guy who is not getting the playing time they want and know from the get go they want something different. Then the guys that enter later may have had a new transfer come in that pushed them further down the depth chart or had a coach leave later in the cycle.
I think all in all, 45 days after a hectic season is totally fair to get some time away, let coaching decisions and changes play out and still give student athletes time to make a well informed decision. I would think that's why the spring window is only 15 days. By the end of spring ball you should have the information you need to decide to get in the portal or not and it doesn't need to take a month and a half.