Yan had an easier path to the belt than Suga though. Yan went through some lower level guys, including washed Faber, and then fought Aldo, who hadn't ever won in the division, for the vacant belt.
At least Suga had to actually fight a top fighter in Yan himself.
I always liked that when Yan won the belt he immediately started talking about wanting to prove himself against only top fighters. Didn't want to have gotten the relatively easy path and then just cherry picked more easy fights. Dude wanted all the hard stuff.
Let's compare resumes pre-title fight - I'll rate the opponents in difficulty from 1-5 (1 being relatively easy, 5 being as tough as it gets):
Ishihara > 1
Son Jin-Soo > 2
Silva de Andrade > 3
Dodson > 3
Rivera > 4
Faber > 3
vs.
Ware > 1
Soukhamthath > 1
Quiñónez > 1
Wineland > 1
Vera > 3 (lost)
Almeida > 1
Moutinho > 1
Paiva > 2
Munhoz > 3 (no contest)
Yan > 5
Basically Yan fought progressively tougher guys up through Rivera and then circumstantially got a title shot off a Faber destruction which was kind of the result of Faber playing hardball; he had just come back out of retirement and finished Ricky Simon in a main event in a minute and told the UFC he wanted to fight for the title. They saw Yan as the future champ so they said OK, beat Yan and we'll give you title shot, and he went and got obliterated worse than he's ever gotten obliterated except against Aldo in the WEC.
They were hand-picking opponents to make Suga look good from the beginning and throughout his career until Yan - slow, short, relatively unskilled or limited strikers with no wrestling whatsoever so that he could style on them and get highlight reel finishes. The two times he got real steps up he lost to Vera on the perennial nerve injury and then eye-poked Munhoz in a fight where he lost the first round and it ended in a no contest. He showed he was worthy of fighting elite contenders in being competitive but clearly losing to Yan, but to get a title shot off what is pretty much a universally agreed upon loss (to the point where we have to question why the judges gave him the win) is far more outrageous than destroying a name/legend in Faber when the division was short of contenders.
It worked out in Yan's favor that the top of the division ate itself alive during his come-up; TJ and Cody had their two fights which ruined Cody, then TJ tried to drop to FLY and ruined himself against Cejudo, then Cejudo fought for the vacant belt against Moraes and almost lost before getting a washed Cruz and retiring.
So he fought 2 of the top 10 from the start of the year (Rivera was 5, Dodson was 8), they probably didn't want to waste Yan in a fight against Assunsao who fights very negative/defensively, there weren't a lot of options at the time once Cejudo vacated they needed to make a title fight to keep the division moving. If anything Aldo was the one who didn't deserve the title fight, he was 0-1 coming off a loss against Moraes (regardless if you think he won or not, they literally gave him a title fight off a loss). I don't see any reason to give Assunsao or Lineker or Aljo (at that time) a shot over Yan.