As for the landlord - clearly taking a very, very short term view. If they had any sense, they'd realise that sucking as much money as is possible out of these businesses now, thereby inevitably putting more independents out of business, would lead to a less desirable parade long term where, 5 years down the line, they'll have problems renting out their units at those prices.
Areas like Lordship Lane render high unit rents because they are desireable shopping/socialising locations with good footfall, gained through a decent mix of chains, independent shops that draw in those with disposable income as well as locals, and restaurants/take-aways/bars in th evening to extend the hours of use. HOP Parade will never be Lordship Lane, nobody is seriously aiming for that, but it could develop into a more sustainable shopping and socialising destination for residents if both the council and landlord (s) had any interest in supporting that idea.