Not too long ago, the Telegraph speculated that the terna being presented to Rome for the Westminster succession consisted of Archbishop Vincent Nichols, Archbishop Peter Smith and Bishop Arthur Roche.
Since then, Archbishop Nichols has commited his unfortunate faux pas on Radio 4, but Archbishop Smith has contributed materially to the cancellation of the LMS Mass in Cardiff.
Meanwhile, as I mentioned here, Bishop MacMahon, the Dominican Bishop whose priests like him as much as if he had been chosen from the secular clergy, has suddenly torn into Paddy Power's lists.
Now, I'm not a believer in post hoc ergo propter hoc, but it is possible to speculate that the terna was received in Rome and a relatively junior curial official got straight back to the Nunciature in London: "you can't seriously expect us to put up a terna without a single religious"; only for a new terna to be sent to Rome, excluding one of the three on the list, but adding Bishop MacMahon. (Rabbit hole: I wonder if the curial official was French; he might appreciate a MacMahon.)
Idle speculation: that's all this is.