That's not really a motivation. That's a goal. What is his reason for screwing over the Federation? One Vulcan failed to save his planet in time. How did that lead to wanting to take down the Federation? (Legit question, as it made no sense at the time, and I haven't watched it since it came out).
Spock destroyed his world, so he wanted to destroy Spock's. Vulcan and Earth obviously.
But Spock didn't destroy Romulus. Romulus was being destroyed regardless of Spock's intervention. Spock merely failed to save the planet, but nobody on Romulus managed to save the planet either. It was a flimsy motivation at best.
Not a fan of the film here... but Star Trek: Countdown makes his motivations a easier to swallow.