I think that’s a good theory.
I have some additional theories:
1. The memo and all the related repercussions from it have taken up all of his time.
2. He is in grave danger from his enemies now that they have been exposed. The danger is real and sobering. (Not that he wasn’t already sober and serious. But knowing what kind of threats you are exposed to has got to have an effect, even on someone as strong and savvy as Trump.)
3. The “acerbic and unnecessary” tweets have fulfilled their purpose. When he has another purpose they would help with, he may resume them.
Agreed.