2. When the Mueller report was about to be released, Attorney General Barr wrote a memo to Congress that purported to summarize the principal conclusions. Trump and Republican supporters seized on this to claim Trump was exonerated. In fact, Mueller explicitly stated that he did not exonerate Trump. Further, in a subsequent letter of his own, Mueller stated that Barr's memo "did not fully capture the context, nature, and substance" of the investigation. (Washington Post article here: https://www.washingtonpost.com/world/national-security/muell...)
There are many more findings, but I tried to be concise in response to the specific claim that there is "nothing there".
When the investigation began and Mueller was appointed, Republicans praised him. (C.f. Fox News article: https://www.foxnews.com/politics/robert-mueller-appointment-...). Now they claim the investigation was either unlawful, or that FBI investigators were criminals, or similar. One does not need to take my or anyone else's word for what Mueller's team reported. You can get the redacted report from the government or even Amazon, and read it for yourself. You can also get the Senate committee's report from the government and read it for yourself. It is clear to me (and should be clear to anyone who has read the report or followed the story) that it is a flat-out lie to say there is "nothing there", and that Trump supporters have shifted from welcoming a fair investigation into Russian interference to attacking the investigators. And that's where we are now.