Ephedrine is the basis for many different decongestants and was widely used in diet pills in the form ephedra, and in many OTC stimulants (Max alert etc).
Methamphetamine can be produced by reducing ephedrine or pseudoephedrine. Since ephedrine is used in decongestants you can start with something like sudafed, extract the ephedrine and move on from there.
Many companies are moving to other things than ephedrine for their otc meds because of the stigma that has been attached to it. In some places Oregon, Iowa and Oklahoma have limits or require prescriptions for things containing ephedrine to combat the meth problem
crank is just a generic term for any sort of amphetamine or methamphetamine.
With regards to it being "the drug" who knows, its been around forever and tends to come and go throughout the years.
