We didn't really, steel is a phenomenal material at retaining strength at high temperatures with minimal long-cycle damage and was well industrially established at the time.

The issue with fusion and especially tokamaks is the triple challenge of mechanical loads + radiation loads + high heat flux. There's really no material known to mankind which can maintain the necessary high-temperature strength, while moving enough heat out of the reactor to keep it economical, without critically degrading in a matter of weeks/months due to fast neutron irradiation (let alone decades, as is standard for nearly every other thermal energy source). Hence, the heat sink will need to be replaced regularly.

Add to that the fact that fusion companies are essentially giant bubbles of debt owed to venture capital currently and you don't have a formula for a successful and cheap energy source.

But anyway, we already have fusion energy and it was probably partly used to charge your phone! It comes from the big floating fusion reactor in the sky, only requires a few panels of silicon, and is the cheapest and greenest energy source in existence.