In 2008 mortgages were handed out like free candy to people who were likely to default. Then they were securitized and a lot of financial institutions invested in them. When investors realized the mortgage securities were much more risky than had been originally believed, the whole thing came crashing down.
Today, people getting mortgages are scrutinized very heavily, and they can actually afford them. A lot of the offers are cash anyway.
The cause of increased house prices today is fundamentally a shortage of housing, compounded by high construction costs for new housing, low mortgage rates, and buyers’ increased preference for more space because of the pandemic.
None of those factors is suddenly going to disappear in a way that would cause housing prices to burst like a bubble. We may see a slow price decline as those factors get sorted out over the next few years, but that would not be a bubble bursting, it would just be an adjustment.