Continuity mistake: Peacemaker and Bloodsport are following Amanda Waller through the female section. There are two girls at the table in the center, one with patchwork colorful skin, the other whistling at them. When it cuts to a close-up, neither is in the appropriate position; the whistler's hand dropped and the Kaleidoscope, who already got up, still has her forearms on the table. (00:20:40)
Other mistake: Javelin already appears amongst the deceased (red layer) on the monitors, but only intermittently, in different shots his status is normal - at the very least he should have the 'critical condition' brown overlay that TDK has. (00:14:00)
Continuity mistake: In the suicide mission on the beach, Flag makes a run for it behind Harley who just ducked behind a rock. Harley is in a dark corner; Flag dives by her, and the camera angle changes showing her into the spotlight. Sane later when TDK's arms are floating and pass by them in bright light. (00:09:55)
Continuity mistake: Blackguard is panicking because of 'the werewolf' but Rick Flag interjects that he's 'harmless'. He then has to add that he's not -that - harmless, having slaughtered a couple dozens of kids; when the camera angle changes before he says that, the actors have changed positions. For instance, Margot Robbie had her hands clasped together before her chest, then she has them in her lap. (00:05:45)
Character mistake: David Dastmalchian is the Polka-Dot Man, hyphenated in the comics, and in the end credits of the movie. Then again, when Waller threatens to kill everyone off, the name of the character appears in print as Polka Dot Man, no hyphen. (01:49:40)
Answer: It's a combination of various reasons. Will Smith wasn't available to reprise his Deadshot role, so there was a shift in the story. King Shark was intended to be in the first film, but the CGI was too extensive, so they went with Killer Croc. In this film, they took the opportunity to bring in King Shark as the "monster" character. But, this film isn't really a sequel or reboot. Basically, this is a new storyline with new characters, and many of the previous characters are just not in the film, with no exposition on what happened to them, and they may not even be part of this film's "universe." The fact that some of the actors play the same character in both films only serves to muddle the concept of this film not really being a part of the previous film's continuity.
Bishop73