All those things you're talking about are literally just one team playing better than another, not exactly what I think he meant by "things going for them".
An example of "things going for them" would be winning the toss on a deteriorating wicket, or playing a touring side that had their only warm-up game washed out, or having your opposition's leading fast bowler injured half way through an innings.
Playing well and making a hundred, bowling better, not dropping catches, someone who's been injured in the past not getting injured --> these are not the same kind of "things going for them", it's just playing better.
I'm pretty sure that's the implication. The way Howe_zat said it, he said BD can only win if:
> Tamim, Shakib, Rahim score runs
> Mehdi and Shakib take wickets on a pitch that suits them
> They win the toss
And like, 2/3rds of that is basically saying 'If BD play well, they win'. Of course if a teams key players perform they win, just as if they don't perform the team loses. It's kind of how cricket works. BD are not unique in that sense.
I don't think the Toss is that relevant because, as we see here, you can bat second and win in these conditions if you are good with the ball on Day 1. Lyon did what I expect Mehdi to be capable of - rip apart a side on a Day 1 spinning pitch with the new ball. I don't think the toss is as crucial as it is being made out to be. This myth existed with playing India in India until teams kept winning tosses, batting first and still losing. These are similar conditions and I think the same theory applies.
Aus lacking prep is definitely an advantage that BD got, ut basically all sides lack any real prep before they tour overseas now days anyways. No one wants to prop that excuse up for when SL or WI or BD lose overseas. A side getting to have proper prep pre-series is considered a luxury, not a pre-requisite, and therefore a lack of prep isn't some advantage in a way that is extremely unlikely and unique to the situation.
I'll give you that BD got fortunate with Haze getting injured midway. That was definitely lucky. But do you really think BD lose that Test if Haze hadn't pulled up lame at that point? He bowled 15 wicketless overs in the first innings, and by the time he pulled up hurt BD already had a 50 odd run lead. Cummins only bowled 14 overs in that innings anways as Agar and Lyon did most of the work. They even drafted in a third spinner here instead of a second quick. They were fortunate, sure, but that wasn't a match-defining moment.