The “as well” here is significant. The Sadducees had already been planning the death of Jesus (#11:53). He was a potential leader of a rebellion and they were scared that because of Jesus, the Romans might remove their privileges, money, and power. Now they plan to kill Lazarus, in addition to killing Jesus. It seems that the prophecy of Caiaphas (#11:50) that “it is better for you that one man die for the people” must now be expanded to be two men (emphasis added). One was not enough and it must now be two. So it is with evil; it continues to grow and grow.

John 11:53  So from that day on they plotted to take his life.

John 11:50  You do not realise that it is better for you that one man die for the people than that the whole nation perish.”

The desire to kill Lazarus seems quite strange in light of the fact, which the chief priest recognized, that he was just raised from the dead by the command of Jesus. Perhaps they thought if he and Jesus were dead, then there would be nobody to raise him again?