Here's a quick explanation.
It is very important that information given to the skippers and to the people on dry land has the same content and the same timing.
We can therefore avoid situations where shore teams would give extra information to their skippers if they know more than sailors at sea.
Also, Vendée Globe skippers are sailing solo, they are not part of a crew.
Receiving the rankings is an important part of the skipper's daily rhythm ad routine, they're looking forward to it.
Skippers have asked to receive enough rankings releases every day to know enough about the fleet's evolution but not too much so they don't have to focus too much on that.
A good balance has been reached thanks to the experience of the previous editions.
Then why 5?
5 daily rankings allow sailors to get enough information to follow the race without having to spend too much time analysing the data they receive.
5 daily rankings allow sailing fans on dry land to follow he race wherever they may be.
5 daily rankings make it possible to keep some suspense between two rankings releases and to make sure the Vendée Globe remains exciting for three months. Three months can be a long time.
5 daily rankings allow the race organisation team to implement the adequate process for each rankings release.