When Bnei Israel left Egypt we read that Pharaoh’s servants had a change of heart and said: MAH ZOT ASINU, “…what is this thing that we have done, that we sent them away…”. (Ex. 14,5) Their complaint is strange for they were the ones who early in the series of plagues urged Pharaoh to send them away.
The reason they acted thus and had a change of heart was because this is when they first realized what the Israelites had done for Egypt. When the Bnei Israel were in Egypt they were not appreciated. It was only after they left that their true value was recognized.
Many times in the history of the Diaspora Jews lived in various countries and helped build up the economy of the country and their society and civilization. When the host country saw how successful the Jews were they decided to place restrictions on them and often banished them from the land. After decades went by and the countries saw their economy and general welfare had degenerated they realized they had made a mistake and invited the Jews to return.
We have seen history repeat itself in our times. European countries all aided the Nazis to destroy their Jewish populations. Without admitting it, they realize what a great asset the Jews were and they are all making an extreme effort to invite them back.