I don‘t think Leanne or Jake thought that Frankie was a Traitor at all - they just wanted a bigger share of the prize money. Sadly I do think they believed Alexander was a Traitor.
Going forward, I think future contestants will now always take it down to 2 players for a bigger slice of the prize.
The only way to stop the ”greed” element in future series is to put in a new rule...
If all the Traitors have been banished in the final and the players continue to banish, then for every Faithful they banish the price pot gets halved each time. If this rule had been in place, I think they’d have still banished Alexander but they would have then split the prize 3 ways with Frankie, unless they TRULY believed she was a Traitor.
For example:
The prize pot was £94,600.
Split between the remaining 4 Faithfuls they’d each have won £23,650 - still a nice sum.
Banish Alexander, the prize pot is now £47,300. Split between 3, each get £15,766.
Banish Francesca, the prize pot is now £23,650 so the 2 winners receive £11,825.
I wonder how it would have played out if that rule was in place? It would banish the chance of them deliberately bamishing Faithfuls for their own gain.
Under current rules:
4 Faithfuls £23,650 each
3 Faithfuls £32,533 each
2 Faithfuls £47,300 each.

There is zero incentive to stop at 4 even if you truly believe you’re all Faithfuls.