WASHINGTON — American spy and law enforcement agencies were united in the belief, in the weeks before the presidential election, that the Russian government had deployed computer hackers to sow chaos during the campaign. But they had conflicting views about the specific goals of the subterfuge.

Last week, Central Intelligence Agency officials presented lawmakers with a stunning new judgment that upended the debate: Russia, they said, had intervened with the primary aim of helping make Donald J. Trump president.

The C.I.A.’s conclusion does not appear to be the product of specific new intelligence obtained since the election, several American officials, including some who had read the agency’s briefing, said on Sunday. Rather, it was an analysis of what many believe is overwhelming circumstantial evidence — evidence that others feel does not support firm judgments — that the Russians put a thumb on the scale for Mr. Trump, and got their desired outcome.

It is unclear why the C.I.A. did not produce this formal assessment before the election, although several officials said that parts of it had been made available to President Obama in the presidential daily briefing in the weeks before the vote. But the conclusion that Moscow ran an operation to help install the next president is one of the most consequential analyses by American spy agencies in years.