Consider below scenario in RAFT algorithm.
Would the other followers vote for the new candidate and elect it as the leader, while the previous leader is also still healthy?
"Would the other followers vote for the new candidate and elect it as the leader, while the previous leader is also still healthy?" the answer is yes - voting does not depend if existing leader is healthy or not.
According to raft white paper (https://raft.github.io/raft.pdf page 4), the follower without hearing a heart beat will become a candidate - it will increase the term and will request votes. And other nodes will have to vote yes as all conditions are met. In fact, even the leader will vote yes and stop being a leader in case they receive such voting request.
This is the sequence of events:
Raft, and many other similar protocols, do not have a concept of strong leader - which means nothing stops the cluster to swap the leader even if the leader is healthy.
If raft protocol is implemented as the paper describes, this is a common issue that a disconnected but alive follower keep initiating new elections on every reconnect. This is happens as the disconnected but alive follower keeps becoming the candidate, increasing it terms - as they can't win the election while disconnected. So when they actually reconnect, suddenly their term is larger then the current one of the cluster, hence new election happens (they won't win it as they don't have latest logs).
In practice, it is common to have "pre candidate" check - the candidate checks if it has connectivity to majority of nodes before bumping up its term number. This approach prevents unnecessary election when the network is not stable.