Mass trees cutting around Handicap Association, along the driveway in front of Blk 98 Whampoa Drive

On 24th Mar 2018, around 8:30am, we were awoken by the loud electronic saw sound. My 3 daughters were shocked to see the healthy trees in front of their room's window were being cut. This happened in Whampoa neighborhood along the driveway in front of Blk 98 Whampoa Drive, surrounding the Handicap association.. We got to know from the workers that they were told to cut the trees mark with "X". We have countered more than 10 trees with mark "X" along that short driveway on that day excluding the ones (2-3 trees) that were already cut. Till date left with 6 trees mark "x".

QUESTIONS??
1) How can all these trees be sick at one go??
2) At what stage is a tree considered too weak to hold itself and is dangerous to the public?
3) Could it be the soil problems? If so, no new trees can be survive and cutting trees is not solving the root cause of the problem. Treat them.

Even there are new plants, no similar trees that can bloom flowers like before and it will take more than 5 years to become mature. Trees are also life, like my daughter said, why not treat the trees? Can we find the cause? If human are sick, we are being treated, why not the trees? It's already very hot in Singapore. Worst part is that this activity destroyed the natural habitat of the birds and squirrels. No more nice unique yellow birds chirping early in the morning.. I personally saw a squirrel running around the premises unable to find their usually home.
How long can we protect the trees here, the nature here and the global warming?