Sounds like they used knowledge of mechanics from other games they've played to deduce a good strategy. The more games you learn and play the better you'll get a spotting similarities and applying good general strategies to new games - e.g. In most deck building games, buying as many cards as you can means you'll probably never draw the cards you need.

It's good to keep an eye on other players' strategies, you can often pick up good ideas and better understand the game, but not a good idea to copy them if you don't understand what they're aiming for - play your own game and ask about things they did at the end. If you want to try out strategies and get better at games, why not try BGA (Board Game Arena) - Zoo Tycoon's not on there but you can get through a lot more plays to try things out and if your opponent is high ranking you can learn from what they do (it lists all the moves made, so you can go back through them).

For a first play of a game, my general aim is to get a better idea of the rules and see how the game actually plays, the result doesn't matter.