Indonesia has 1,340 ethnics. All ethnics occupy their home territories but some ethnics migrate to some areas in Indonesia. Recently, there are 10 major ethnics in Indonesia. Javanese is the largest ethnic groups in Indonesia.

Source of Data : DINAMIKA PERKEMBANGAN ETNIS DI INDONESIA DALAM KONTEKS PERSATUAN NEGARA Agus Joko Pitoyo dan Hari Triwahyudi, Fakultas Geografi, Universitas Gadjah Mada, Yogyakarta
This the development and migration of ethnics data in Indonesia. Javanese people are more than 95 million people. Most Javanese people live on the island of Java. Statistic in 2010 shows that Javanese people in Jakarta are 3,453,453 people West Java 5,710,652 people, Central Java 31,560,859 people , East Java 30.019.156 people and Yogyakarta 3,331,355 people.

Another large island that has more than 40 % Javanese people is Sumatra Island. So, Javanese population is more than 95 million people in all over Indonesia. So it is not surprising that most Indonesian presidents come from the Javanese ethnic group.

The origin of the Javanese Ethnic group

In my writing, I would like to present two theories. They are from Eugene Dubois and Von Hein Geldern.
Refference : https://perpustakaan.id/suku-jawa/

1. Eugene Dubois

He is an archeologist. He found ancient human fossils on the island of Java which he named Pithecanthropus Erectus and Homo Erectus. The DNA test shows that has no much differences between the current Javanese people with the fosil. Thererefore, Javanese people are the indegenous people of Java island.

1. Von Hein Geldern

Javanese people are southern Chinese or Yunan people who migrated to the island of Java 2000 years before Christ and 500 years before Christ.

Pic : pic : https://era.id/culture/107056/mengenal-7-kebiasaan-orang-jawa-secara-umum

Java experienced civilizations that rose and fell with the rise and fall of large kingdoms centered on the island of Java such as Ancient Mataram, Singasari, Majapahi, Demak and finally Islamic Mataram.

The kingdoms in Java also invaded the archipelago which became the forerunner of the State of Indonesia.

In conclusion, Javanese are the largest ethnic group in Indonesia. The historical background is the reason why this ethnic group is the majority in Indonesia.

Source : DINAMIKA PERKEMBANGAN ETNIS DI INDONESIA DALAM KONTEKS PERSATUAN NEGARA Agus Joko Pitoyo dan Hari Triwahyudi, Fakultas Geografi, Universitas Gadjah Mada, Yogyakarta
https://perpustakaan.id/suku-jawa/