The clauses in your lease which expressly forbid this sort of activity would actually probably count as the "first you heard from your landlord that he didn't want you AirBNB'ing." It's not like you were unaware of them - you wrote that you "had flouted the same clauses" before.

Now that you were cranking tons of guests through for personal gain, you were surprised when your landlord took exception. If I found out that somebody was blatantly disregarding the rental agreement they'd signed with me for commercial gain, they would not be getting a friendly "hey brother, can you please stop?" phone call either.