“ Their future will lie in your willingness to share your spending data with businesses that have partnered with these new banks, receiving deals based on your spending patterns and behaviour.”

This wasn’t made clear to me when I signed up, just goes to show that banks can make more selling your data, than selling you their services.

I very much doubt that - Monzo's whole plan was to do this and they still couldn't pull it off and become profitable with it.

I think the future of challenger banks is in offering competitive services at much lower overheads compared to the legacy banks. Starling Bank is a good example of that IMO, and as far as I know they're profitable.