So I've considered this a fair bit.
1. IF MM randomly assigns players to each team with considerations only for nation, same botes spread across teams, tiers etc, then theoretically every game you join has a random smattering of skills on both teams yes? That means that over time, your win/loss ratio will depend on your skill. IE if, with reference to yourself only and being placed in random battles with 11 randoms on your team and 12 randoms on the other (or x-1 on your team and x on the other where x is a number of players per team when the game is not 12 a side) of equally randomized skill, then over time, your win/loss becomes an indicator of how effective YOU are at affecting the outcome of a battle - as, over time, YOU are the only constant in a sea of randoms (heh, SEA of randoms).
So if we rank players with a skill rating from 1-10, 1 being no ability to change the outcome of a battle and 10 being ultimate ability to change the outcome of a battle and assume some kind of standard distribution, then you will come across pretty much zero 1-2's and zero 9-10's with most of the people you play with and against being 5's and 6's but with plenty of 4's and 7's.
This means over time, you can easily be randomly allocated skill 4 and 5 players on your team while the enemy team can randomly consist of skill 5 and 6 players. This can happen randomly - it is possible. It is possible for MM to be both random and unlucky in assigning you teammates.
So assuming that you are a skill rating of 5.5 (arbitrary allocation) and you end up randomly assigned to an unluckily rolled team of 4's and 5's then your total team skill might easily be something like 4.5 (all skills averaged) while the enemy team may be lucky and have 6's and 7's meaning their overall team skill is 6.5.
Imagine playing 10 games in a row with all tier 4 ships on your team and all tier 6 ships on the other? How would that play out?
So yes, MM can take SOME things into account while attempting to create games but it can't take player skill into account and considering what I've suggested above, this can mean a string of defeats through no fault of your own.
2. I have a mate who loves casinos and the roulette wheel in particular. I don't condone gambling or encourage it (*runs off to Buy Tirpitz to see if it betters my win/loss ration :p ) but I sat beside him one night while he was at the wheel. There was beer and flashing lights and he's good company so I was happy. He favoured betting on a red or black outcome that night. A simple 50/50 chance. I watched as the previous rolls board filled with black results. The screen showed maybe 15 previous results (more maybe!?) and they were all black but as we had been sitting there watching, we knew that more than what was being showed had been black. The dealer (spinner whatever you call her) was as dumbfounded as everyone else.
In short - MM is random. You can be randomly assigned good and bad players and this can happen over a long period.