Isaiah 36:17

“Until I come and take you away to a land like your own land, a land of corn and wine, a land of bread and vineyards.”

But he is offering a treaty and therefore recognises that he must lay out the terms fairly. If he did not do so it would rebound on the honour of his master, for treaties were treated very strictly. So he now acknowledges that his offer was not strictly true. Many of those listening must rather expect deportation, but he makes it sound as appetising as possible. They need not fear. Even if they are deported they will be taken to a land of plenty (he omits the details of how unpleasant the deporting will be).

As all knew, deportation of important people in the case of rebellious states was Assyrian policy. Its purpose was in order to weaken the leadership (by removing many of them) and to divide the nation, thus making them more amenable. (2 Kings expands on the offer, and includes the offer of ‘life' instead of death).