Maybe it’s his way of poking the Stones in the eye. They don’t want him using the song. But they don’t have a say - Trump’s campaign paid for it and has the right to use it. You might say you can’t always get what you want.
Former Rolling Stones manager Alan Klein’s company has the rights to many of the Rolling Stones songs and will sell use to anyone.
Remember, at one time Michael Jackson owned the rights to the Beatles songs until Paul McCartney bought it back.