Another possible explanation is that there are more people/entities with large amounts of cash, or less people with enough income to buy a house, or both.

Or maybe all three.

That's not a cash offer unless the property being purchased is far lower in purchase price than the profit off the sale of the first home (i.e. due to downsizing, or moving from a much higher to much lower cost area), in which case it is a different housing submarket, and there could be a net local demand increase.

This includes nearly all senior citizen purchases, but it's also a surprising number of 40/50-something wage earners who bought in HCOL areas around 2010, saw their $800K homes appreciate to about $2M, have paid the mortgage down to about $450K (or paid it off entirely, using stock price appreciation), and also have a couple million in appreciated stocks from saving abundantly during the 00s and 10s and enjoying the stock price appreciation.

Or if you are buying an $80k property with the proceeds, it is so different than the sold property - either much smaller or less desirable in some way - that you are buying in what is effectively a different market altogether.