I had no doubt whatsoever that Izzy was going to win that fight.
Neither one of them had ever attempted a single takedown in their UFC careers and they both like to strike.
Adesanya was a world class kickboxer before he transitioned into MMA. If it's going to be a pure kickboxing fight with MMA gloves, the result shouldn't be shocking. There's nobody in the UFC, regardless of weight class, that can rival Izzy on the feet in a straight kickboxing fight.
Paulo Costa's only path to victory was to mimic Gastelum, but I'm not sure he has the tools. Alternatively, if he could have pressured Izzy against the cage and limit his mobility, then to muscle his way into dirty boxing and clinchwork, then maybe.