Sen. Mazie Hirono (D., Hawaii) said Russian president Vladimir Putin "must be really happy" about the results of special counsel Robert Mueller's investigation into Russian interference in the 2016 election, which found no conspiracy between President Donald Trump's campaign and Russia.

"So just because there was not enough evidence for a criminal charge of conspiracy does not mean that this very cozy relationship that Donald Trump has with Vladimir Putin—who, by the way, must be really happy that this came about—that this kind of cozy relationship that is not good for our country, in that it's not transparent, will continue," Hirono said during an appearance on MSNBC's Andrea Mitchell Reports.

Mueller determined Trump did not collude with Russia during the 2016 campaign, and refrained from making a judgment on whether the president tried to impede the investigation.

"The Special Counsel's investigation did not find that the Trump campaign or anyone associated with it conspired or coordinated with Russia in its efforts to influence the 2016 U.S. presidential election," Attorney General William Barr wrote in a letter to Congress. "As the report states, ‘[T]he investigation did not establish that members of the Trump Campaign conspired or coordinated with the Russian government in its election interference activities.'"

Barr and Deputy Attorney General Rod Rosenstein found there was "not sufficient evidence to establish the President committed an obstruction-of-justice offense."

Trump said on Sunday that it was a "shame" the country had to go through the investigation.

"It's a shame that our country had to go through this," Trump said. "This was an illegal takedown that failed and hopefully somebody is going to be looking at the other side."

On Monday, Trump said Mueller acted honorably during the investigation, and repeated that the report should be made public if the attorney general agreed that was the correct course of action.