What did I do wrong with my olive oil cake?

First attempt and first time trying it ever. It looked great in the oven but it fell shortly after I took it out. I turned it over to decorate it, so the bottom part looks more like cake and the top part looks totally compact. The only thing I changed in the recipe was using nuts milk instead of regular because of intolerance, but usually that’s not a problem. It tastes good though, so we ate it anyway. What did I do wrong here?

Recipe: https://theviewfromgreatisland.com/lemon-olive-oil-cake/