I am sure this is in defiance of Trump's threat to Jerome Powell. But to be honest, the rate should have been cut, judging by the trend of the US inflation rate.
Although Jerome Powell is the Fed chairman but he does not have sole authority to make decisions on interest rates. Like any agency in the US, lowering or raising interest rates requires a vote and according to the news, there were 9 votes in favor of maintaining interest rates and only 2 votes in favor of lowering interest rates.
If it is as simple as you stated, Trump would not dare attack any FED Chairman, but he knows that if he wants it done, it would be done. Fine, it's all about the decision and the votes of the Board of Governors of the Federal Reserve (Board) and the Federal Open Market Committee (FOMC), yet the position of the FED Chairman is powerful and influencing. He has the power to convince his colleagues to vote for a rate cut. Who knows if he is the one influencing the rate hold just to annoy Trump more?