Tax Lien Sale Courthouse Steps - Really weird - Why did this happen????

[Russell R Massey]

Atlanta.
Referencing a small corner property, 45'x20', zoned Residential. Planning says nothing can be built there (well it could but it is VERY VERY VERY unlikely it would be approved per zoning). Long established residential neighborhood and used to be a corner store. Completely demolished and no slab left for 40+ years. Vacant for 40+ years.
In other words, anyone who buys it is buying the right to pay taxes on an unsellable lot forever. 
I had looked for the relatives of the deceased owner before with no success. 

It went up for tax sale Nov. 2023.

Somehow, a quitclaim was made from the sole heir just 5 days before  the tax sale - and recorded in the deed book the day after the tax sale.  

The tax debt was about $7k on the property. The property tax lien sale amount was $80,000 on the courthouse steps!!! So, they are close to $90k in. I own the surrounding lot and was the second bidder. Based on similar lots, it should have gone anywhere from not purchased to 3-9k. 

Can anyone clue me in to what the heck is goin on here? 
I will be glad to send you a $50 Amazon gift card for a really plausible theory. 

Prior Theories:
It could be turned commercial (no)
A residence could be built there (no)
They bought it to sell to me at a profit because I am the only one who cares about this. (Plausible for a $5k win. Not plausible for $80K+back taxes which gets up to $90k. If I would have paid more, I would have bid more)
They made a mistake and thought it was a different property (there are several with the same roadname but not the same Parcel - and this was professional who was bidding on several properties)

Can anyone clue me in to what the heck is goin on here?

[Kevin Sobilo]

@Russell R Massey, a few thoughts:

1. Zoning ordinances in some areas don't mean much. In my market zoning ordinances often make 95% of existing residential lots nonconforming where nothing could be built within the ordinance. So, they become somewhat unenforceable as they need to allow some uses. So, setbacks etc are often waived as long as the use is in line with the character of the neighborhood. 

2. What is the area like? If its urban at all perhaps an ancillary use such as a paid parking lot?

3. I suspect that the property MUST be allowed to be used. Zoning cannot take all uses away, otherwise the municipality would have to buy the property. Its like eminent domain but initiated by the owner because they will claim an "unlawful taking" of property by denying all uses for it.

4. I'm not familiar with your state's tax sale process but in my state if the tax debt is paid prior to the sale (EVEN MINUTES PRIOR) then the sale is voided. I have been at auctions where people in the audience claim the owner is right that moment paying the taxes. They skip that property and send someone to verify and come back to it later after they know if they were paid or not to avoid a situation like may have happened in your case. So, perhaps they didn't pay the $80k amount and the buyer at that sale was refunded. In which case the new owner would only be into the property a small amount.