It would be a little harsh if that was the reason for the ban, we would have to wait for a mod to clarify.
I interprete Pliagarism as an attempt to copy someone else's work and pass it off as your creation, in order to get acknowledgement or some other form of benefits, or to boost your post count.
There is nothing harsh about that. He copied texts and passed them off as his own, and that is clear plagiarism. Even if his intention wasn't to do that, but the act is considered plagiarism anyway.
It was never my intention to plagiarism someone others stuff
Well, then you could simply paste the link to the source from where you picked them up, which would not make it plagiarism.
i didnt even hear about such a rule
No one would come to you and read them (the rules) out loud for you. You need to read them so that you don't break them and get punished for it.
Below is the rule you've broken, and it is in the rules, which are supposed to be read by everyone using the forum:
33. Posting plagiarized content is not allowed.[e]
Complete list of rules:
https://bitcointalk.org/index.php?topic=703657.0