RAFT election restrictions

I'm learning Raft from scratch with the Raft paper, and I can't understand the leader election process. I read in 5.4.1 that a leader needs to have in its log all the committed entries of the cluster:

Raft uses a simpler approach where it guarantees that all the committed entries from previous terms are present on each new leader from the moment of its election, without the need to transfer those entries to the leader.

Raft uses the voting process to prevent a candidate from winning an election unless its log contains all committed entries.

But later on, it is said that a candidate holds all the committed entries if it is at least as up-to-date as any other log in the majority. And the mechanism to determine this up-to-date is comparing the index and term of the last entries. The log with the higher term on the last entry will be more up-to-date.

Couldn't that lead to a situation in which a leader was elected without all previous committed entries? For instance:

In this case, if server 4 failed, server 2 could become leader, since it has an entry with a bigger term than the majority. But it wouldn't have in its log the two committed entries from term 2. Is that right? I am misunderstanding something but I can get what it is...

The question is, how did the logs get to that state in the first place? It's not possible.

So, it looks like:

* Server 2 is leader for term 1
* Server 1 is leader for term 2
* Server 2 (perhaps) is leader for term 3
* Server 4 is leader for term 4

But server 2 couldn't have been the leader for term 3 because it couldn't get votes based on the fact the last entry in its log would have been from term 1. If another server was leader for term 3, it must have written an entry for term 3 in its log if there's an entry from term 3 in server 2's log. But if there was another entry for term 3 in another server's log, a server with entries from term 2 could not have been elected since there would only be two of those. Even if server 3 had entries from term 2 in its log, it couldn't have been elected at that position because there would still be three other servers with entries from term 2 at higher indexes in the log.

So, I think you need to describe how the cluster got in a state in which server 2 could have won an election that would put an entry from term 3 in its log at index 4. It's important to note that the election protocol is not just about terms, it's also about indices. If two servers' last entries have the same term, the server with the greater last index is considered more up to date.