Like it or not, the transfer portal has become a huge factor in how college football rosters are constructed from one year to the next. Some programs are much better than others at utilizing it.
Just ask Heisman Trophy winners and former transfers Baker Mayfield and Kyler Murray how important the portal can be.
For the most part, the transfer portal is for scarcely used players who are looking for a chance to show what they are capable of doing. For whatever reason, things didn't work out at their first school, and they need a change of scenery just to see the field.