MacBook dead from liquid damage - that turned on once. Any hope?

Using rice or any other form of desiccant will NOT work. That is because, after the liquid has evaporated, it will still leave trace elements behind that can short out electric circuits inside your Mac notebook. If you power up the Mac, there is a good chance that these short circuits can further damage it. The only potential way to "fix" this would be to open the notebook and remove any of these trace elements BEFORE you apply power to it again. This is definitely not a DIY endeavor for the average notebook user.

Without removing those traces any, further power being applied, will make any hope of recovery even less likely. Sorry.

Gulp, I wish I could offer some hope, even slim hope, but I fear there is extremely little hope that a fix would be simple or that cheap.

https://www.macofalltrades.com/shop/apple-laptops/refurbished-macbook/?_bc_fsnf=1&Year=2017

My question is, would the circuit short immediately and never power up or is it possible for the circuit to run for a while and short later?

Yes either, the dryer it is the more the latter is likely.

As another comment stated, rice will unfortunately not help in resolving liquid damage from your Mac. Because the damage has likely already been done to the internal circuitry of the machine, my best advice to you would be to put that money into a new system. I know this is certainly not the ideal outcome but it sounds like your Mac is beyond reasonable cost or effort to repair.

BDAqua pretty much covered it. Again, without your Mac throughly inspected and properly cleaned, every time you use it, you are just gambling that nothing will go wrong.