The Pacific Northwest club walked out to a record 69,724 crowd at Century Link Field and were thoroughly outplayed in the opening stanza.
Toronto controlled possession but were unable to translate their dominance to the scoreboard as Seattle held on until half-time.
And speaking to Tribalfootball, Australia international Smith said the break helped his team settle after a tough first-half.
He said: "We didn't start the game as well as we wanted. I think the occasion got to us with our fans watching.
"We were erratic at times and didn't control the game in the first half. But at half-time we had a chat to try and calm it down.
"Then we got the first goal and we kind of just went from there. And once we had three goals you're pretty happy."
Currently on loan from Bournemouth, Smith said it was a "dream come true" to win a major trophy after a testing few seasons in England, which led to his omission from Australia's 2018 World Cup squad.
"It's amazing for me personally, as I said before its been a tough few years I've had not playing regularly," continued the left-back.
"And missing out on the Socceroos at the World Cup it really hurt me so for me to come to Seattle and win a Championship in a year and a half is a dream come true."
There was no extended celebrations for Smith however, as the 24-year-old was heading straight to international duty after the game.
"I got to leave in about 45 minutes! I'm going to play for the Socceroos in Jordan so I've got to get my flight."