The evil Dr. Vandertramp was convinced that truly great villains needed some formative, life-changing experience to turn them away from the natural human inclination for mild goodness (the kind that limply "does the right thing" only when it's not inconvenient and can't be said to truly align with GOOD or EVIL) and toward an existence bent on scheming, sabotage, and wickedness both surreptitious and blatant.
To his enormous disappointment, the children who had once been at least nominally in his care were now grown and were pursuing various forms of lukewarm mediocrity. He felt that he had failed them but wasn't sure what else he could have done for them.
Now Dr. Vandertramp's children were beginning to have children of their own and, bafflingly, were perfectly willing to include the nefarious grandfather in their lives. This meant that the pressure was on: these interactions might be his last chance to corrupt a generation who would carry on the Vandertramp legacy, and he refused to fail the children this time.
And now for a vaguely thematically related comic: