How in the world?!?

Playing quick africa game.
4 players. I capture player A's capital. Hes eliminated after I hold it two turns.
Few turns later another player captures that city after I abandoned it.
Next turn the previously eliminated player REJOINS in that city and magically has 66 tanks...

There's a game option that allows you to rejoin a game after you die. When you rejoin a game, the longer the game has gone on the more reinforcements you get to start off with maxing out at 100 reinforcements. Chances are he rejoined as a neutral country nearby and had enough money to spam out 66 tanks with the extra reinforcements he got. To prevent this you can propose a vote to change the turn limit you can join to 0 under game settings, or before the game is started disable rejoining in the advanced area. Rejoining is automatically set to allow whenever you start a game and has to be turned off if you don't want it.

Ah I see. That almost sounds like a strategy for jerks.. Lol. I did notice he changed proposed that rule change right after he rejoined...

Allow joining until turn limit was probably pretty high already then and he wanted to propose it so it be even higher. So like maybe you could join up until turn 25 and he wanted it until turn 99. You know just encase he died again. It comes down to a vote and if everyone else votes for it then yeah, sucks but happens.

Most good hosts will set it so joining doesnt occur pass say turn 5, sometimes not even pass turn 0, which means after picking is done you can't join. Many do forget though to disable rejoining itself, and so if for some reason someone proposes to change that and it goes through then yeah you get latejoiners/people rejoining.