I doubt that your Gmail password was hacked by brute force because it's very strong and Gmail should have blocked your account after multiple failed login attempts.
The most prevalent method to harvest login credentials is via an email supposedly sent to you from a friend or colleague who has already been hacked. You receive an email and assume it was sent by them and the email has a link that says something like "click here to view the photos/documents". You click on it and it asks for your email address and password. Because you know and trust the person who sent the email you happily enter those details.