Isaiah is part of the Torah, the Old Testament.

Written… roughly between 740 BC and 680 BC.

Hell, as modern many Christians imagine it (eternal place of torture amidst fire and flames for those that do not accept Jesus) does not exist in Judaism.

There were/are varying interpretations…

From the Torah itself, you have Sheol, which is basically like a dark and dreary cave, a place of forgetfulness, which everyone goes to, and your soul/consciousness just kind of slowly fades away into nothing.

Relying more on the Talmud, you also have Gehinnom, a place of punishment for sinners which can be a place of fire and brimstone, or it can be more like a place for reflection and review of your sins… usually your sould only goes there for 12 months.

Gehinnom, as a concept, largely came about after the Second Tenple was destroyed in 70 AD… Christians would use parts of this idea as a basis to make their idea of Hell worse and worse as time went on.

tl;dr Isaiah was written hundreds of years before the New Testament existed, probably about a thousand years, maybe more, before the modern Christian Hell was formulated.