The Exynos 9285 has been proven inferior to the Qualcomm Snapdragon 855, so is it any surprise that Samsung is switching to the Snapdragon 865 for the Galaxy S11 series? Europeans are still set to receive the lesser Exynos version though, according to multiple sources.
https://www.notebookcheck.net/Reports-claim-that-Samsung-has-dropped-Exynos-in-all-but-one-region-for-the-Galaxy-S11-and-Galaxy-S11.447131.0.html
Not sure about phones, but tablet from 2016 uses exynos and is still undefeated in overall battery performance.
It makes sense. Exynos is an inferior Snapdragon, especially when it comes to the GPU.
Samsung used Exynos to cut costs, but since the Snapdragon 865 is produced by Samsung's foundries, there's no more economic incentive to use an Exynos.