The government withdrew from the housing provision role that it had previously to a much bigger degree than its international peers. That resulted in much less of this very important part of the housing market.
It doesn't have to be a massive piece to reduce price pressures by a large degree because people who now have access to this housing aren't participating in the the process of bidding up housing in the market. That's going to pull down prices for rentals and houses more generally, as part of a general increase of supply.
We need to make sure that everyone has access to housing. More social housing will improve that access and will help reduce prices across the entire housing market.