Why is Envisat considered a potential trigger for the Kessler Syndrome?

Envisat is considered as a potential trigger for the Kessler syndrome because of its size, it is a big satellite and is operating at an altitude which has a high concentration of space debris. If you consider its mass, shape and volume, you will know it's indeed a potential trigger for the Kessler syndrome. Any collision between the Envisat and any object in the space can lead to the creation of more space debris in the orbit. And as a result, it increases the possibility of more collisions.

The space is filled already with enough space debris and any further occurrence of collision between the Envisat and any other space object can cause more space junk which in turn create more collisions. If this happens, we are likely going to experience Kessler syndrome, a situation where the Low Earth Orbit will have an increasing density of space debris. And this might prevent future space operation because there would be high rate of more collisions between any object that is being launched into the space and the cloud of smaller space debris.