Because he knew that years of complete and utter bullshit obstructionism was coming his way. They used the lie to get seats in the 2018 election. They used the lie and obstructionism to an unprecedented level - there are still Federal Appointees a full 2 years in that haven't been cleared due to the Democrats running out the clock on every single nomination. It's utter bullshit and Trump was smart enough to know what it was way back then, when dullard motherfuckers like you still don't know reality from television.