Every once in a while you come across a Youtube video where somebody 'discovers' some interesting or rare collectible, then tries to start it up right away after replacing the battery.
That's so bad, because there can be so many things which have seized up, plugged up, corroded, drained out, etc., that trying to crank or ignite the engine causes huge amounts of damage.
Anything which has sat for years really needs to have all relevant parts and fluids replaced, and the rest cleaned and adjusted as appropriate, before trying to start the engine. Especially if it was put away dirty in the first place.
https://www.youtube.com/watch?v=f0CragRdCVI
https://www.youtube.com/watch?v=34CRCZWwNhM