The snap judgments piled in before the race was called: Eric Cantor’s looming upset, arguably the most shocking in modern political history, owed to his support for immigration reform. Conservative activists, boiling-mad at the prospect of what they viewed as amnesty for undocumented workers, had surged in Cantor’s Richmond-area district to turn him out. The challenger himself, Dave Brat, even acknowledged the issue played a major role.

But as observers spent Wednesday sifting through a campaign that had received minimal attention up until election night, that picture muddied. As it turns out, Brat, an economics professor at tiny Randolph-Macon College, had scored with a much more potent, and nuanced, line of attack. He filleted the House Majority Leader by sending him up as a crony of big corporate interests seeking to preserve themselves through big government in Washington.

“All the investment banks up in New York and Washington or whatever, those guys should have gone to jail,” Brat told a May 7 gathering of the Mechanicsville Tea Party. “Instead of going to jail, where’d they go? They went onto Eric’s Rolodex. That’s where they all are, and they’re sending him big checks.”

It was a clever bit of jujitsu for a candidate whom Cantor was overwhelming 25-to-1 in campaign fundraising. More significantly, it stoked the darkest suspicions of voters already wary of Cantor’s leadership responsibilities in Washington, felt as absenteeism back home: The incumbent had lost touch, the line went, because he was off courting billionaires in Silicon Valley and on Wall Street, then representing the interests of the super rich back in the corridors of the super powerful.

There was more than a kernel of truth to Brat’s critique. Cantor’s rapid ascent in national Republican politics was fueled by his remarkable fundraising ability. And that ability — in Cantor, or anyone else — owes ultimately to shamelessness in asking for money and a sales job pledging the funds will support common interests of the donor and the party. “A lot of these guys don’t want to make the ask,” one connected Republican lobbyist said. “He never minded.”

It showed. Cantor’s leadership political action committee (called Every Republican Is Crucial PAC, or ERIC PAC for short) has out-raised every other fund of its kind during this election cycle. That success allowed Cantor to rain unrivaled largesse on his colleagues. This cycle alone, he’s used the account to distribute more than $1.6 million to fellow Republicans. That sum dwarfs leadership PAC giving by any other Member of Congress, including Speaker John Boehner, the next most generous, who’s dolled out $715,000 over the same period, according to figures from the Center for Responsive Politics.

Where did it all come from? Four of Cantor’s top five contributors this cycle hail from the financial services industry, by far his biggest supporter over the course of his career. And he earned the support by distinguishing himself as an unflagging champion of Wall Street’s priorities on Capitol Hill. As the Obama administration and Democrats in Congress have pushed to end the capital gains treatment of investment profits earned by fund managers — the so-called carried interest tax provision — Cantor became the its most outspoken defender. More recently, he opposed one of his own when the Republican chairman of the tax-writing House Ways and Means Committee proposed ending the preferential treatment in a tax code overhaul.

There have been smaller favors, too. Two years ago, Cantor scuttled a provision in a broader transparency measure that would have forced lobbyists selling market-moving information to investors to disclose their clients (a maneuver Brat seized on in his campaign).

That Cantor served as an essential cog in the machinery linking the Republican party to its big business base is clear enough from the roster of industry lobbying groups that stepped up to support his campaign. The American Chemistry Council alone plowed $300,000 into airing TV ads in the district.

Brat made sure the support cut both ways. “Eric is running on one set of principles. He’s running on the Chamber of Commerce and the Business Roundtable principles,” he told the crowd in Mechanicsville last month. Indeed, Cantor’s loss, and his subsequent decision to step down from leadership at the end of next month, means those business groups have lost a critical ally as they struggle to wrest the initiative in the GOP back from Tea Party elements.

In the wake of his defeat, Cantor canceled a speech he was scheduled to deliver Wednesday to the National Association of Manufacturers. Cantor has been a leading promoter of one of the group’s top priorities — reauthorizing the Export-Import Bank. The typically noncontroversial measure has galvanized Tea Party opposition, with activists panning it as corporate welfare. And the critics now have a foothold with House Republicans. Among those opposing the bank is House Financial Services Chairman Jeb Hensarling, a Texan now mulling a bid to replace Cantor in House Republican leadership.