A bit of both, and also a sprinkle of the interest rates going from almost 20% at points in the 80s, to essentially 0% today, meaning people can afford to borrow a lot more at once, and home sellers profiteering off this.
Just to give an example: a 30 year mortgage for $300,000 at 4% is about $1400 per month where a 30 year mortgage for $100,000 at 17% is about $1400 per month. That can explain a 3x multiplier in the home price to income ratio assuming that people purchase based on what they can afford monthly.