The Muller investigation was a huge success, even thought it didn't find any collusion by Trump. For almost 2 years it gave special prosecutes the power to put anyone that did business with Trump, supported him politically or was close friend of his, under microscopes and expose any activities they were involved with that weren't 100% legit. As a result of this investigation many of his supporters, business partners and friends are in big trouble for activities that would have ordinarily gone UN-noticed, many just for lying about what they knew.
The word is out, if you support Trump, or do business with him you might find yourself under a microscope. I'm sure many potential supporters will be scared away by that possibility.
Of course Democrats couldn't be more pleased since I think most didn't really believed Trump was personally working with the Russians, but how might they feel if the next time they win the Presidency their candidate is similarly accused and EVERYONE associated with and supporting them is put under a microscope? Personally I think we have much better ways to spend $25 million dollars.