When Mace Windu decides that he has to kill Palpatine, he is holding his lightsaber inches from Palpatine's throat.
Given that a lightsaber can cut metal, he should have easily been able to kill Palpatine by just thrusting the lightsaber forward.
This would finish Palpatine without giving him or Anakin any time to intervene.
Instead however, Windu swings his blade back to slice at Palpatine, allowing Anakin to intervene and save him.
Why does Mace Windu swing back instead of simply slashing forward, when slashing forward would have guaranteed Palpatine's death and avoided any risk of interference?