Beneficial Insertion Mutation

E. Coli bacteria require 2 mutations in order to utilize salicin. In a lab, these two mutations were observed to occur and produce a strain of E. Coli that utilized Salicin.

"In growing cells the two mutations occur at rates of 4 x 10(-8) per cell division and less than 2 x 10(-12) per cell division, respectively."

That's pretty heavy odds, right? So I wonder how it could have been observed... Well, Another paper which cited this one stated that mutations occur at higher rates in stressful environments. Who says evolution is against the odds?