One Advantage of Trump: People Avoid Messing With Crazy People

   Appearing unpredictable can be an advantage: if Smith is unpredictable, and Jones is rational, Jones is likely to mess with Smith less. If Smith is predictable, Jones might tend to walk right up to the line, if you get what I mean. But if Jones doesn't know where the line is, he'll be inclined to stay well back from its furthest reaches (as he judges them).
   So tactically speaking, it can be an advantage to appear unstable even though you aren't. Suppose Putin is thinking "Hm...what if I just grab Estonia? Estonia looks tempting." If, say, Obama is in office, Putin might do the calculations and decide: "Obama won't blow up the world over Estonia... At worst, he'll kick me out. So maybe it's worth a try." Suppose, however, Trump is in office. Putin might very well think "God knows, that lunatic might just blow up the world over Estonia."
   However, when you appear unstable because you are unstable...well, in those cases, the tactical advantage is probably cancelled out.