The mainstream view is that whatever Trump says at 5 AM on Twitter is spontaneous and, therefore, “authentic.” As a result, it may presage changes in policy, and it is definitely newsworthy.
The cynical view is that Trump views his tweets as a way to entertain himself and engage the base, but nothing more. They may in some way be “authentic,” but they don’t represent government policy, and they are not newsworthy.
The problem is that the world has trouble telling the difference. It is perfectly possible that the North Korean government could interpret provocative statements meant solely for the base as a desire to go to war, and act accordingly. It is also likely that casual statements of opinion on events in other countries may damage our relationships with those countries. Just ask Theresa May.
The bottom line is that Trump craves attention, and believes that keeping the world off-balance is a benefit to him and the US. The down side to his Twitter account, however, far outweighs its advantages.