I suspect retiring Tennessee Senator Lamar Alexander spoke for many and perhaps most of his fellow Republicans in the chamber when he said that while the impeachment managers from the House of Representatives proved that President Trump improperly manipulated government policy regarding Ukraine for his own political advantage, his behavior was not sufficiently egregious to meet the high threshold for removal from office—and that, especially with a national election ten months away, the decision about the next president should be left to the voters.
Ironically, Alexander's perspective wasn't that different from that expressed by Nancy Pelosi, the Speaker of the House, until her fellow Democrats forced her hand to proceed with impeachment following the revelations about Trump's attempt to pressure the new Ukrainian president.
While the opinion polls suggest the impeachment has increased the public's concern about Trump's behavior, it probably will be a while before there are enough survey data to indicate whether it has had any significant effect on state-by-state support for his re-election. However, I think one thing that is clear is that Pelosi and the Republican leader in the Senate, Mitch McConnell—two of the shrewdest strategists to lead their respective chambers in many years—both played the political cards they were dealt very well.
Although Pelosi no doubt hopes the impeachment has weakened Trump and thus will increase the likelihood that the eventual Democratic candidate for president will be elected next November, her primary objective has clearly been to maintain her majority in the House of Representatives. It was no secret to anyone that absent a seismic change in public opinion, there was no possibility the Senate would vote to remove Trump from office. However I suspect Pelosi calculated that the very failure to do so would energize Democratic Party activists to make the effort in November to get their less-committed voters to turn out. When turnout is high, both nationally and in many of the states, the Democrats tend to do well, but they face demographic and structural obstacles to getting out their vote: young people and members of minority groups who historically have not been highly motivated voters, hourly workers who must sacrifice wages to stand in line at the polls, and rules in some states that create bureaucratic obstacles to demonstrating eligibility to vote.
McConnell no doubt hopes to see a Republican continue to occupy the White House (although I suspect he would prefer it to be someone other than Trump), but like Pelosi in the House, his primary objective is to hold onto his majority in the Senate. For that—and, indeed, for his own re-election in Kentucky—he simply couldn't afford to take any action during the impeachment proceedings that might antagonize what might be called the "Trump wing" of the Republican party, a critical core of enthusiastic voters who themselves typically aren't sufficient to swing an election but whose support is necessary for a Republican to be elected in many states. McConnell had to deliver for Trump in the Senate trial and he did: by avoiding testimony from potentially embarrassing witnesses and scheduling a final vote as quickly as the Senate rules would allow. Presumably he can now count on Trump to reciprocate by doing everything he can to help the Republican senators who face difficult re-election campaigns. While Trump's national approval rating has never gone above 50 percent, his support among voters who identify as Republicans remains very high—and there is currently little reason to think that will change before the November election.