Because Rider ended up seeing her in a negative light, perhaps?
Rider was just a massive hypocrite whontried to pretend his way of kingship was somehow more valid than Saber's despite the fact the whole point of the Banquet was just to have 3 kings equally say their way of kingship was valid.
Islander was never trying to save Saber.
In fact, he is equally as hypocrticial, or in fact far worse, in that he wants to use the Grail to incarnate (become enfleshed) so he can attempt to conquet the world again.
Rider was just a massive hypocrite whontried to pretend his way of kingship was somehow more valid than Saber's despite the fact the whole point of the Banquet was just to have 3 kings equally say their way of kingship was valid.
Islander was never trying to save Saber.
In fact, he is equally as hypocrticial, or in fact far worse, in that he wants to use the Grail to incarnate (become enfleshed) so he can attempt to conquet the world again.