Currently Max is out of position in BC's defense. He's a little undersized to be a classic 4-3 DE. NFL teams might see him as someone who might thrive in a 3-4. Another year at BC wouldn't have helped him hone 3-4 skills, so if he impresses in the workouts and interviews he might get drafted in the later rounds. I am sure Montel Harris's injury was in the back of his mind too. Leaving now -- while he is still healthy -- allows him the chance to play professionally. If he returns and gets hurt, that might not be an option. Finally, maybe he needs the motivation. As we've said, college football is a grind. Especially when you are not winning. If he wasn't passionate about returning to BC, it is best to move on and challenge himself.
At this point, he is a long shot to get drafted. With fewer rounds of the NFL Draft the Undrafted Free Agent path is more common, but certainly not easier. A breakout season next year might have raised his stock a bit. He might also have played his last down of football. There are no guarantees in the sport. If he loves to play, giving up a final year at BC might be a mistake.
For BC, this is not good news. Holloway was not an elite player, but he was very consistent and someone we could have used next year. It also makes you question the morale and motivation if players are leaving on the slight chance of getting drafted.