What was the key factor in thomas edisons success in dising the light bulb

Thomas Alva Edison was a famous American inventor, best known for developing many devices like motion pictures, sound recording, mass communication and electric power generation. When Edison developed the incandescent light bulb its key factor  was the carbonized cardboard. After many experiments, he discovered that it was a suitable element for his filament as the carbon filament would glow without burning.

i confess that there are several parts of this constitution which i do not at present approve, but i am not sure i shall never approve them: for having lived long, i have experienced many instances of being obliged by better information or fuller consideration, to change opinions even on important subjects, which i once thought right, but found to be otherwise. it is therefore that the older i grow, the more apt i am to doubt my own judgment, and to pay more respect to the judgment of others.