When sorting by Virtual Memory, the bigger on top, and showing the ones that use most memory, when the process that uses most memory is killed, the view goes to the lowest memory ones instead of staying showing the bigger ones.
I can confirm the behaviour, which I find rather annoying.
ksysguard is no longer maintained, in Plasma 6 there is the Plasma system monitor for this task. If your issue still happens with the Plasma 6 replacement, please re-open and we can move this bug to the new product, thanks!