If I'm reading the blog post correctly, his Twitter account was compromised via GMail. If his GMail account had not been compromised, they wouldn't have gained access to his Twitter feed (which was the true target of the attack).
They would still have been able to compromise his iCloud account and thus destroy the data stored on his computers.
Unfortunately, I think that in this particular case, having two-factor auth on GMail wouldn't have helped. His account was compromised by having a password recovery email sent to his iCloud address. Presumably, password recovery bypasses two-factor auth.
In this attack and the earlier CloudFlare attack, the attacker took advantage of inappropriate recovery email settings. While it's reasonable for consumers to enter recovery emails, I think that professionals should avoid enabling them. When a @gmail.com sends recovery mail to @me.com (or vice-versa), the attack surface is greatly increased.