Complex sentence: In 1989, NBC changed the format of the show, removing some of the Smurfs from the forest and omitted the Smurf village and adopted a lost in time format similar to "The Time Tunnel", and then ultimately cancelled it due to decreasing ratings.
Split into simpler sentences: In 1989, NBC changed the format of the show, removing some of the Smurfs from the forest and omitted the Smurf village. Using some elements from previous seasons, these were adopted to a lost in time format similar to "The Time Tunnel", and then ultimately got cancelled due to decreasing ratings.