Sorry but you are totally glossing over the known facts of this...
Despite regular inspections, a tree fell over a year ago and could quite easily have killed someone
After this, the council inspected all 77 trees and found 22 are diseased but given that it is a pretty infectious disease, it is quite likely others also have early stage disease.
They then spent a YEAR publicising this in their emails, magazine, local papers and by writing to residents to inform them of this.
The trees are currently 160 years old, and that species of tree has a life span of 150-200 years, so even the ones which aren't diseased are very near the end of their natural life and likely to start becoming dangerous.
The decision to remove and replace them all in one go means the trees can all grow at the same rate and recreate the current effect, within a generation.
Most importantly, it means there isn't a MASSIVE risk to the safety of people using that part of the common from random falling branches.
How on earth can you think stringing out a few more years of the trees is more important than people not risking getting killed. Which, by the way, happened on Clapham Common a few years ago...
I don't want a massive chunk of my council tax being disproportionately spent on a daily maintenance schedule because some NIMBYs don't understand that trees have a natural lifespan