The increase in supply we hope to see because of vacinations is from sellers who are also buyers. That is a net zero for the market. True supply is new construction and deaths; people live longer, boomers are not selling.
The US is short about 4,000,000 homes - that is the new construction undersupply since 2008 when many builders went bankrupt or scaled down. We have started building more, but the wrong kind (at least here in Milwaukee it's only luxury homes) and the cost is going up quickly (materials, supply chain.. not only lumber, which has quadrupeld).
Demand is comming from a shift in demographics: millennisals are now the largets group of home buyers, 82 million, 39 years old - they are not going back to rent. That is actual demand, that consumes additional houses. They don't have one to sell.
I talk about this on my YouTube channel a lot, we have entered a new phase. This is not a temporaty situation, this market is here to stay. Ask anyone in CA how that works.
We have lost the ability to make new homes on scale, we don't have the trades, we don't have the land, we don't have the necessary zoning for high density, affordable Sf with city sewer and city water. Everything, at least in the Milwaukee area, is zoned for large SF on 1-5 acres with pricate well and spetic - 500 to 700k. That is not what we need. We need volume under 350k and it is physically impossible for a builder to do.
A lot of factors influence the market, like you have pointed out @William Allen - interest rates, goverment policy, money supply, stimulus, forbearance etc - but in the end it comes down to supply and demand. And that will take a while to balance out.
Capitalist markets are self regulating between supply and demand; of course we will expand supply, but that will take time (need more young people in trades..). The only other solution is that we reach a balanced market through price - one prices have gone up far enough, demand will be reduced and more people will rent, because it's cheaper. Right now thats still not the case in Milwaukee - much cheaper to own a home than to rent. I expect this to change over the next years.