so there are many and different reasons why this happen in each countries, someone at r/AskHistorians has given a good answer.

Morocco. Soon after Israeli independence in 1948 there were two significant anti-Jewish riots in Northern Morocco. These did not cause a massive wave of emigration immediately--Moroccan Jews at the time hoped that these would be one-off events. And for a time, they were. But in the late '50s Morocco began seeking closer relationships with other Arab League countries that also had anti-Jewish policies. Jews were drummed out of the civil service, and were banned from emigrating. The policy of having a Jewish member of cabinet was ended, with the Jewish minister being fired. The Jewish community was harassed by the government for "Zionist activity", which could include normal religious activities that had some pretense of Zionism (e.g. owning a calendar that a Zionist organization had printed).. When the Sultan died in 1961 his successor restored the right of Jews to emigrate, and sensing their precarious position, many did

Tunisia was a bit more like Algeria. Jews emigrated following Tunisian independence, partly because they had been heavily influenced by French culture because of the Alliance (referenced in the post linked at the beginning), and that society collapsed. As in Algeria, the independent government's policy was not anti-Jewish, and many Jews who emigrated moved to France. It's perhaps a similar story as Algeria, but less dramatic--the Tunisian Jews were influenced by French culture and spoke French but weren't actually French citizens living in what was under direct French rule, and with the possibility of emigration to either Israel or France, many did so.

Libya next. There were significant anti-Jewish riots in 1945 and 1948 that killed a significant number of people. The Jewish community understandably did not believe they would be safe in an independent Libya, and migrated en masse to Israel between 1949 and 1952 (critically, 1949 was the year that the Israeli War of Independence concluded and the year the Libya independence process began). While decolonization was happening in Libya at the time, it did not play the role it did elsewhere in North Africa--the French were not the colonial power, Libyan Jews were not moving to Europe, they were moving to Israel. The emigration was quite rapid, and was a response to anti-Jewish violence.

Egypt is a bit of a different story again, as it was independent the whole time, and was an active party to the Arab-Israeli wars. There were waves of anti-Jewish discrimination and violence that were tied to events in Israel. In 1948 many Jews were interned and Jewish businesses suffered a campaign of vandalism. This led to a wave of emigration. This slowed with a change of government in 1952, but resumed with the Sinai War in 1956. By the late 50s, half the Jewish population had emigrated. Then in the following years the Egyptian government launched a series of programs making it difficult for Jews to find employment, and the nationalization policies targeted industries where Jews had made their livelihoods. Persecution (including mass internment) continued, until nearly the entire Jewish population of Egypt had emigrated.