In his efforts to obstruct justice, Donald Trump has intimidated and harassed key witnesses to his treasonous Russian connections. The problem is that he doesn't threaten to kill them, so he isn't having them silenced. He just pisses them off by firing them.
In Russia, many of these peope would run a big risk of getting killed, or even be killed. What Trump doesn't realize is that firing someone doesn't make the person disappear. That was the case on his pseudo reality show "The Apprentice", where Trump would say "You're fired!", and they were out of the show. In real life, however, a fired person can still be interviewed, and will have all the more reason to turn on Trump.
Apparently, Trump is too stupid to understand reality.