I'm guessing the process was that the new boys, Wenger and Gazidis met to discuss next season and Wenger would have asked something like 'do you all still think that I am the best man for the job?'. The feedback was probably nicely phrased but was ultimately 'no, we think we need to move in a new direction but won't force it upon you'. Wenger then decided that it was best to step down.
Was that a 'sacking'? I don't think so.