Complex sentence: The main site at Meyrin has a large computer facility containing powerful data processing facilities, primarily for experimental-data analysis; because of the need to make these facilities available to researchers elsewhere, it has historically been a major wide area network hub.
Split into simpler sentences: The main site at Meyrin has a large computer facility containing powerful data processing facilities, primarily to analyze data from experiments. Researchers need remote access to these facilities, so it has historically been a major wide area network hub.