It is normal to say:
I believe/think that X is more important than Y.
But is it normal and more importantly correct to phrase the sentence like this:
X is more important than Y I believe/think.
I have searched about this matter and found that they are two independent sentences, and since the second one is short, a comma is not needed.
However, I didn't find examples in that specific structure.
Also, I have noticed that an "as" can fit greatly before the second part of the sentence, so does that mean it also can be omitted with preserving the sentence meaning and validity?