I think ultimately Marvel wanted to create a controversial story that they thought people would be interested in. Saying that Kraven might return is certainly a move that will get people talking. And the reason would have been because sales on the title were slumping and they wanted to increase them.
While saling have been falling, your reasoning has no legs. Marvel's been doing controversal stories to get people talking and get attention since the comic line began anew 50 years ago.