One thing we know Trump is legitimately good at is manipulating rubes.

“Thank you for your attention to this matter" is actually quite subtle; it's got "you" and "your attention" in the same sentence, making it feel like he could be talking to you personally rather than as a group (compare e.g. Biden's common "May God bless you all").

"Hey, Trump thanked me for my attention, there's a guy who respects and values my time and opinions, and the fact that he says it in every one of his messages only means that he really does care what I think."