Hard to put the entire blame on Rudy for this. He had to stay down when KAT screened for Antman, otherwise there would've been a wide-open layup, which then freed up KAT to come back over the top, forcing Conley to switch onto him. Conley then made the mistake of motioning to Rudy to come up and take KAT, and in that split second of indecision, he and Rudy both ended up going to KAT.
As soon as Conley was switched on KAT he should've just made that his primary assignment, and not give mixed signals on who he was going to guard.