It's actually technically in the subjunctive, which often matches the past simple, but not always. For example, in a conditional sentence, we would say "if I were you," but in past simple, it would be "I was." Unfortunately many grammar books don't explain this.

Yes, you’ve got it💪🏼 If I won the lottery… If I had more free time… If I could swim… Not however that the verb “be” can act irregularly. For example: If I were you… If I were taller…