When is it considered polite to announce an attempt for a win?

I played a Spelltable game a few days ago, the host had named the lobby as seeking "PL8" decks.

After getting drained down to 3 life due to an [[Authority of the Consuls]], I had to bring myself down to 1 to remove the enchantment with [[Masked Vandal]]. I proceeded to combo off and win that same turn. I had announced my intent to win on that turn. My opponents were tapped out trying to beat each other.

Once i won, the host of the game immediately closed the game after sarcastically exclaiming "wow you won on 1 life dude good job" in that very dissatisfied tone of voice you might be familiar with.

Was I wrong to keep quiet about my boardstate until the turn I won? It sounds ridiculous to me to have to declare my intent to win a full turn cycle before my actual attempt. I wasn't asked about my boardstate, two of my combo pieces were in play for several turns prior, i was just waiting for the last piece that i eventually got. Is this an ironically unwinnable situation because of what i did?