The Ranking System

Our ranked team lost our first match then we won the next four matches and we ranked at bronze five. I'm just wondering if anyone out there can explain what happened. Like I personally feel that with only one loss in the placements and ending on a four win streak would have gotten us placed anywhere but bronze five. I mean, I understand that the teams we went up against were not good but it just doesn't make sense to me. We lose our first match so they drop our match making rating. Fine. We win the second one, I'd expect our mmr to go up at least a little. And after three more wins to not have our mmr increase at all leading to our wins having no effect on our placement. I feel riot could find a way to improve this for next season, but any help would be greatly appreciated in at least understanding what happened.