If you don't use Two-Factor Authentication, and you have a public profile, the question isn't if your account will be compromised, but when . Apparently, for Mr. Mattheij, when was today. The next question is "how do you safely recover your account". Hopefully this is a straightforward process, considering you have access to the email account associated with your Twitter account. Of course, Twitter needs to make sure…
There is no way that my account password was compromised without a much more elaborate hack of Twitter, either that or someone social engineered them to change my password.
Believing you weren't/couldn't be phished is a great way to get phished again...