Complex sentence: It was created in May 2002 on a request of a Czech editor of Esperanto Wikipedia; however back then Wikipedia ran on UseMod software and the three pages the Czech one had were lost during the switch to MediaWiki.
Split into simpler sentences: It was created in May 2002 on a request of a Czech editor of Esperanto Wikipedia. The three pages the Czech version had at the time were lost during the switch to MediaWiki.