Can I understand the rejection reason of an article by reading the reviewers' comments?
You can't really tell, unless it's explicit in the referee reports you receive. A referee could well give suggestions for improvements even if they advise rejecting the paper - they don't assume that just because the paper wouldn't appear in this journal it won't appear anywhere. It also doesn't matter whether all the referees recommended rejection - it is the editors that make the call, and that is what stands.