How does raft handle committing entries from previous one?

Question

In raft paper section 5.4.2

If a leader crashes before committing an entry, future leaders will attempt to finish replicating the entry. However, a le

Answer 1

I think the question is that the leader crashed after few followers applied log to the state machine. In (c) in the figure, the Leader has copied the log of term 2 to more than half of the nodes, and then the Leader updates the commitIndex to 2 and sends the heartbeat. And before leader crash, only S2 received the heartbeat and applies the log of term 2 to the state machine .According to the paper, S5 can be new leader by votes from S3 and S4, and try to append the log of term 3 to S2~S4. But, this operation should not be allowed, because S2 has already applied the log at index 2 to state machine. Seems Raft does not cover this situation