Doing terrorism makes you a terrorist, then why it matters if he said "forgive me Allah"? Why did you make that connection?

If he hadn't said anything about Allah he would still be a "potential terrorist" because of what is explained in the article. Which btw, yeah very suspicious, good they detained and questioned him.

Do you understand now why we suspect you are racist?

You could have argued "I meant, someone scribling 'forgive me God' indicates they are going to do something bad, plus points to them maybe being hyperreligious/unstable" but you didn't went with that argument.