My point is that there are hidden favours, some set as early as the start of the season itself. It is sort of as follows.
good season or bad season (pluses or minuses attached to your team)
good season or bad season for what competition (pluses or minuses attached to your team, but those are specific for a competition)
Neglecting the quality difference, the budget, things like that, all teams don't start equally and they are not treated the same way throughout the season; there are favours (or hidden advantages and disadvantages). Those favours influence the 'dices' used for individual matches too - sort of the dices themselves are not same; some have more 5s and 6s on the sides and some have more 1s and 2s. For me, it is just part of the simulation in an attempt to simulate things how they happen in real life.
Your team will still have good chances to win if you have a high quality team and use decent tactics. Else, how would those of like Madflo, Nash and even you yourself, and so on won so much? Like you yourself said, quality is among the first things. Then, you for example, you increased your chances more by manipulating your squad.
So, briefly, as a manager, if we want to win, we should do things to increase our chances (things we can control or have an influence on). Then it is all up to the game and what the game wants or what it planned or calculated for the season as a whole, or for a specific competition or for a specific match.
For example, take my case this season. I won the treble with a team I would describe as more on the average side (I had much better team than that in the past, but failed to even win doubles at times). There were strong and even strong, active opponents in the competitions this season, but in the end my team won all 3. I did not manipulate draws nor did I power trained players to 7-stars or above and so on, but I did things as a manager is expected to do to increase my chance to win, and the the rest was up to the game and its plans. I myself, I anticipated that this season the game will favour my team to win some competitions; sometimes, you can already see how the game set things up to favour a particular team. How about those times where my team won singles, doubles and even went close to win a treble (lost a final) when the team was more like abandoned? The team was abandoned, but had the a decent squad and used a decent formation (those are which are among the minimum requirements), but also, there must be some sort of favour as it went on to win competitions like more on its own (no manager, no training, no condition maintenance and so on). This sort of observation is more evident when it comes to competitions like the Cup and the Champions League; the league seem to do active managers and hard work more justice.