All three are correct.
He beat Reyes taking it easy or not and he got the belt(disclaimer). While I think the "Reyes got robbed people" just hate Jones and would say that anytime Jones won a 3-2 fight(people actually post the Santos fight was a robbery) Reyes fighting Jones close makes the belt something more than paper. But the hard truth is he earned fans skepticism who've known about him for more than a year. If fans considered Bisping a fluke champ, Jan should be considered that, Bisping was way closer to being the champ prior to that fluke KO than Jan was. He got a title shot by KO'ing a borderline top 5 guy who dominated him in their first fight and he'd previously not only lost a title elim to Thiago Santos but to guys like Patrick Cummins and Manuwa. Also before he KO'd Rockhold(who had his hands down)and Corey he hadn't KO'd anyone since 2010 and TKO'd anyone since 2014. He just got a reputation for having KO power overnight that the evidence suggests just was never there.
Here's a list of LHW fighters in the UFC. How many of them would you pick Jan to beat?
Rakic
Jiri
Reyes
Volkan
Thiago Santos(assuming he's himself and that injury wasn't the beginning of the end)
Glover
Here's a list of fighters in Bellator how many of them would you pick Jan to beat?
Nemkov
Bader
Phil Davis
Corey Anderson
The truth is there's a good argument for picking all 10 of these guys to beat Jan not to mention Jones or Ankalaev. Not everyone's going to pick all 10 of these guys to beat Jan but hard to believe someone wouldn't pick more than 4 or 5. Jan is arguably the 11th best LHW fighter in the world not counting Jon Jones. He won a belt but the evidence suggests it was a fluke and there's a lot of guys in his weight class who'd beat him, that's not disrespect that's just the reality. Best fighter I did not put on this list was Anthony Smith. There's enough exciting LHW's now for Jan to prove he's not lucky to be champ and he just dramtatically improved this late in his improve. He'll get the chance to prove that but does anyone really predict he's going to do it?
And Izzy is totally doing a GSP style cherry pick. It's not a coincidence that Izzy decided now was the time to fight the LHW, yeah Jan is just the most challenging/interesting fight and it has absolutely nothing to do with getting to be a champ champ by defeating a very beatable opponent. And in theory Izzy cleaned out his division and it makes sense for him to go up in practice it was almost cleaned out when he became champ him getting a bunch of defenses was something that was easy to predict regardless of how you think he stands up P4P.