We both win.
Contrails, disturbance of atmospheric moisture, occurs at the higher altitudes. Being just water vapor, the trail rapidly dissipates.
Chemtrails, release of chemicals (compounds of barium, aluminum, strontium and others), occurs at mid-level altitudes. Being composed of particulates other than water, they do not dissipate like water vapor, they linger. It takes mixing and air-dilution to dissipate, thus they can often appear to take over the sky, horizon to horizon.
Again, see the earlier vid of the chemtrail pilot for much more detail.
What if the air is cool and humid so that it can’t absorb more moisture. Or what if the air is cold so the vapor freezes into ice crystals. Seems like it could linger under those conditions.
Different atmospheric conditions at different altitudes mean some contrails last longer than others.