Painful, but necessary post-WWI and -WWII population exchanges helped maintain stability by homogenizing religious or ethnic people geographically. India and Pakistan in the late 1940s comes to mind first.
The Ottoman Empire and Kemalist Turkiye effected population transfers with Athens, saddening Greeks in Anatolia (Izmir) and Turks in Greece, but stopping right-wing nationalists from committing outrages and counter-outrages against innocent people.
The people in northen Syria elected to join Turkiye (Hatay Velayet), while the folks in Mosul voted to join Iraq. These were peaceful border transfers, even though for decades Hafez Assad's stamps and maps showed Hatay as Syrian territory.
1914 Armenian nationalists in the Ottoman Empire -- dashnaks I believe they were called -- made a terrible mistake by siding with Imperial Russia in the hopes that St Petersburg would help them achieve a homeland. But these dashnaks misinterpreted previous signals from Russia and the Western powers about "protecting Christians under Islamic rule," as these were just cynically-rendered excuses to attack and carve up the "Sick Man of Europe."
That blunder cost the Armenian people badly which led to their "Nakba," the 1915 genocide when these people were forcibly moved en masse under terrible conditions. This was not a population exchange, but a one-way transfer that killed 1.5m Armenians.
Had the Armenians stayed loyal to the Ottoman Empire and not cause an uprising during the Great War, as a people and nation they would have been saved and the Armenians would have had more to offer in negotiations such as the Treaty of Sevres (1920). The loss of territory, fortresses, and population weakened them; the Georgians and Azerbaijanis managed much better dealing with the Turks and Russians (White and Bolshevik) in the post WWI upheaval.
When Israel was formed in 1948, they proceeded to do to the Palestinians what the Ottomans did to the Armenians in 1915, a population transfer, not exchange, without compensation for lost lands and property.
Like the Armenians from 1919-1923 in the Transcaucasus who were forced to sit at the "kiddie table," Palestinians are similarly powerless today.
But the Israelis had a chance to split the land with the Palestinians, Druze, Christians, and Bedouins, and chose not too. After the 1993 Oslo Accords, a map was drawn to show how it could have been done: drudge.com
Today, PTSD, hard drug abuse, anti-LGBTQ pogroms, constant wars, and an influx of illegal firearms are negatively impacting Israeli society. So, Israel recorded its first net population migration loss in 2024 and folks there are looking at German citizenship. And Israel's ethnic cleansing have turned them into a Pariah nation with a parallel increase in global antisemitism.
Oligarch Governor Jared Polis (D-CO) with a net worth of $400m did this.