Most contracts issued by public universities ask their foreign teachers to apply in writing for a new contract not fewer than 60 days before the present contract expires. It is then up to the university to offer a new contract or not. The reason for the aforementioned procedure is to give the university plenty of time to seek replacement foreign staff if they choose to do so.
If the five foreign teachers there are all leaving, it does not necessarily mean they are dissatisfied with their employer. Maybe those who wished to stay and were liked by the university asked for salary increases that the university wasn't willing to agree to.
Just because a university won't offer an encumbent foreign teacher a new contract does not mean he has been fired. Maybe he never asked for one, and the Chinese side wouldn't offer one in that situation so as not to lose face if said foreign teacher subsequently declined the offer. Or maybe he would attach strings like a big salary increase, which would also embarrass the Chinese side if the president wouldn't sanction that.