1. Did Trump collude with Russians who tried to influence the 2016 presidential election?
No. In Volume 1 of his report, Mueller didn’t mention “collusion,” which is not a legal term. He did, however, find that there was no evidence of a conspiracy, and he therefore exonerated Trump on that count. Still, Mueller concluded that the Russians did interfere, Trump was aware of the interference, he benefited from and encouraged the interference – e.g., Don, Jr. was eager to get and use information on Hillary Clinton – and he didn’t report the interference to the FBI. So, there was no crime and maybe no impeachable offense, but Mueller’s findings will likely inform voters regarding Trump’s fitness for office.
2. Did Trump obstruct justice by impeding either Comey’s or Mueller’s investigations?
Maybe. In Volume 2, Mueller cited numerous acts that could have frustrated both investigations. Trump fired Comey, tried to fire Mueller – but didn’t succeed because White House counsel Don McGahn refused to follow instructions – discouraged testimony, encouraged lying, and dangled (but didn’t actually offer) pardons. Given the evidence, Mueller concluded that he could not exonerate Trump from an obstruction charge. Nonetheless, Mueller would not say whether there was an indictable crime because of a written Justice Department policy that a sitting president cannot be indicted. It would be unfair to charge the president without affording him an opportunity to defend himself at trial. In other words, there may or may not have been sufficient evidence of a crime or impeachable offense; but there was clearly too much evidence to exonerate. Mueller left the criminal charge up to Attorney General Barr; and he left impeachment up to Congress.
3. Since the FBI director serves at the pleasure of the president, could Trump fire Comey at will?
Yes. There are no statutory conditions on the president’s authority to remove the FBI director. He or she serves at the will of the president. But if the president acts with “corrupt intent” – e.g., to impede an investigation into his own conduct – then he can be charged with obstruction of justice. In this instance, by Trump’s own words, hefired Comey because of “this Russian thing.”