What incentives does Iran have to provide nuclear weapons to a terrorist organization?
A state's preeminent goal is survival.
Iran is a state.
Therefore, Iran's preeminent goal is survival.
Conventional arms are one thing, but if Iran provided terrorist organizations with nuclear weapons, it would be giving other states little choice but to form a coalition against it.
Let's assume that Iran does want to supply terrorist organizations with nuclear capabilities. Why haven't they done the same with their biological and chemical weapons programs, which they undoubtedly possess?