Why doesn't Flandel Steelskin have Fire Domain? ONe of his 2E titles is the "Pyromancer" and he has ties to the elemental Plane of fire as well.

2E is irrelevant, as is the Fire domain to Flandal Steelskin.

His dogma reads:

The treasures of life are buried within Flandal’s embrace and only hard labor, dedication and great craftsmanship, as taught by the Master of Metals, can reveal the hidden beauty. Dig mines, extract ores and forge suits of armor, weapons and other items of metal. Strive to refine known techniques, invent new processes and stay physically fit.

As you can see, his portfolio is far more focussed on labour and creation.