What tactic do they employ? That could be a second source of unrealistic success.
I remember that Köln used to be too successful when FM12 was released due to their tacic being more effective in the ME than others by chance.
Also on FM10 Genoa always became a European super-power because in the match engine a tactic with 3 central strikers was vastly overeffective and their manager happened to be the only one at top level to use it.
Well, that's a fairly uncommon tactic at least, so it may well be that the ME favours it (along with its further instructions) for some reason.
I recently read that the ME allegedly favours narrow tactics. The 3-5-2 has only 2 players in wide positions, but 8 in the centre. So if the allegation is true the tactic may make use of an unintended 'exploit'.
It's also down to how much money they have as well imo. When you start off, they have over £1m to spend in transfers and I think they still have over £100k in wages to spend. A couple of strong signings and well it's easy.
In 15 years they made the play-offs twice finishing 3rd & 4th.. In 2019/2020 they finshed 22nd and got relegated, but bounce back straight away winning league 1 and JPT. Now they are a bottom
table team in the championship just avoiding relegation again