Why is that funny? Do you understand what contrails are made of? Water vapour. What is rain made of? Oh, the same. Damp air makes contrails, they are effectively clouds made by the turbulence from aircraft. Natures makes clouds from damp air too, and then it rains sometimes.
Atmospheric conditions. It depends on lots of factors, ambient temperature, air pressure/altitude, the humidity of the air, and wind speed.
If the air is dry, ie low humidity, a jet contrail will dissipate quickly, as nature likes to even things out and the moisture will spread.
If it's humid up there, the air already contains it's fair share of moisture, and cannot take much more from the area of the contrail, so the contrail stays as it is for much longer.
There are no 'fake' contrails, unless you are at an air show, watching an aerobatic display team. They use a variety of devices to make smoke, not least diesel oil released into the jet exhaust.