...I always figured it had something to do with the threat level that group represented. How close they got to the truth of things, or destroying the Shimmer, or something like that...

[He puts a hand to his mouth, thinking.]

Like, if you had the time to slowly turn into a plant, or mess with their heads long enough that they'd lie down and let you finish the job, then there's no need for the extra effort of suddenly smashing everyone together in one big death pile, right?