If God did not force them to leave, He would have requited them in this life (even worse than forcing them to leave). In the Hereafter He will commit them to the retribution of Hell.
وَلَولا أَن كَتَبَ اللَّهُ عَلَيهِمُ الجَلاءَ لَعَذَّبَهُم فِى الدُّنيا وَلَهُم فِى الـٔاخِرَةِ عَذابُ النّارِ
wa law laaa an katabal laahu ‘alaihimul jalaaa’a la’azzabahum fid dunyaa wa lahum fil Aakhirati ‘azaabun Naar