Seisay had consistently underperformed not only the coaches' expectations, but also his own, based on his comments during interviews last season. 

We don't know what might have happened behind the scenes, and in the absence of more info the most reasonable conclusion is that Seisay was one of that large group of players whose athleticism and high school performance simply don't translate into success at this level. I don't fault him for seeking opportunities to play elsewhere and wish him good luck.