Its because its proof the people they wanted to label as conspiracy kooks, are actually correct.
The contrails are nothing but a byproduct of fuel being burnt. They are simply a cloud. I am a 747 captain and I can speak with certainty there is nothing more than a cloud being created by the jet. The two things that you need before a cloud can be formed are moisture in the air and compensation nuclei. The nuclei would be particulates from the jet fuel. It is the carbon is released in the air. If you happen to pass through an area with a lot of moisture the moisture will attach itself to the nuclei and form a cloud. If you ever notice a jet flying overhead and then suddenly start a contrail or stop one is because of the moisture in the air. It’s going into a dryer air mass or a wetter air mass. It forms a cloud albeit a very skinny narrow one. We do not have some sort of stupid switch to start releasing a contrail.