Despite the slogan fixated on by observers — Make America Great Again — Trump won the presidency based largely on a single word: change.
No. Trump won the Presidency by saying bad things ab0ut people his supporters did not like. This was mostly the “3Ms” of Mexicans, Muslims and the Media. Like any demagogue he pandered to fears and prejudices associated with already unpopular people and groups. The most disturbing aspect of it all is that it worked.
Your suggestion for Trump to regain control amounts to establishing sanity in his tweets, and other messaging. Well sure, but even presenting that as the solution suggests the problem. His tweets are not sane, they are not disciplined, they are devoid of reality for a reason. It’s not some random passing thing. It has been a pattern with him for years.
Trump’s tweets appear unbalanced and undisciplined because he is mentally unbalanced an undisciplined. Donald Trump is batfecalmaterial crazy. He believes in things that are not true, to include his own near infallibility. He is not connected to reality.
Until that problem is fixed, the solution you suggest is not feasible, and that problem cannot be fixed. The sanity you seek in his tweets lacks a foundation of sanity to begin with.