That's only for economic profit. Normal profit remains even when economic profit is driven to zero:

https://www.investopedia.com/terms/n/normal_profit.asp

"Economic profit is the profit an entity achieves after accounting for both explicit and implicit costs.

Economic Profit = Revenues - Explicit costs – Implicit costs

Normal profit occurs when economic profit is zero or alternatively when revenues equal explicit and implicit costs.

Total Revenue - Explicit Cost - Implicit Cost = 0

or

Total Revenue = Explicit + Implicit Costs"