Complex sentence: Because of the delay in receiving "Fragments" for exedition's final publication, the leader of the expedition, Joseph Paul Gaimard held Laestadius' work in his private collection until his death in 1858.
Split into simpler sentences: Because of the delay in receiving "Fragments" it was not published in the expedition's final publication work. The leader of the expedition, Joseph Paul Gaimard held Laestadius' work in his private collection until his death in 1858.