Moshe told the whole of Israel when leaving Egypt that if at any point they failed to uphold the Torah in some way, Egypt would no longer be involved. Instead, G-d would choose another nation since Egypt had already served its purpose. After the nation failed through the sin of the Golden Calf, Amalek was chosen as the ikar uma notel kilkul kulam was because they were mekareres ha'kedera. The Nation of Israel would to go into the hands of this new nation to merit the time of the Mashiach and to restore creation. Israel became the exclusive owners of the World to Come after G-d offered all the nations of the world their portion in the World to Come and they refused. This was through the tests of the exodus from Egypt and the splitting of the Red Sea.