I looked into my purchase history. I got tropico 4 as part of a strategy bundle and a few days later on steam tropico 1 2 and 3 were a bundle since i think 4 was still new at that time. This was done back in 2014. If you look at Fanatical right now https://www.fanatical.com/en/game/tropico-trilogy you can get the 1st 3 in a trilogy pack. that exact pack wasn't the same one i got back in 2014. It just happend the 3 games had a discount if you got them in a bundle. Speaking of steam bundles this is the current bundle pack for the whole series up to date https://store.steampowered.com/bundle/1583/The_Tropico_Bundle/ - It has all the games and their DLC's but for some odd reason game 2 is not listed? You may be lucky to see 1 - 4 in a bundle from time to time on humble. Fanatical did have bundles like that too but i don't visit that website as much as i used to. It used to be known as Bundle Stars and when they changed their name that is when i stopped visiting.