A teams wining streak is always links to individual players rating. The more player rating well will usually mean wins for your team, usually O.K.
As players rate well in games 8/9 their morale will increase and bad ratings 4/5/6 their morale will decrease.
P.S. Are there additional factors, I suspect so, some people call it the overnight nightmare syndrome. As with all T11 things it's never cut and dry always a mystery here and there.