It's not the only reason. There is no one reason.
Off the top of my head:
- Pension changes driving some boomers to nest egg in property which drove up prices
- Active destruction of public housing pushing more and more people into private housing which drove up prices
- Tax incentives encouraging property speculation which drove up prices
- Allowance of foreign purchase which encouraged landbanking and laundering and pushed up prices
- New builds failing to keep pace with increase in population limiting availability and pushing up prices
- Volume builders land squatting and releasing less than required to maintain artificial scarcity and push up prices
- Failure to decentralise employment hubs coupled with failure to increase density pushing more people into the same area, causing scarcity and driving up prices