Complex sentence: A project to build a bridge from Chiloé Island to the mainland of Chile was initially proposed in 1972 and was eventually launched under the government of Ricardo Lagos (2000-2006) who launched the project as part of works to celebrate the Bicentennial of Chile.
Split into simpler sentences: A project to build a bridge from Chiloé Island to the mainland of Chile was initially proposed in 1972. Elaboration of the project only began many years later under the government of Ricardo Lagos who launched the project as part of works to celebrate the Bicentennial of Chile.