The DMCA is not a "legislative absurdity." It was embraced by both content owners and internet companies, who sought the safe harbor provisions of the act. From Congress's viewpoint, it was a measure that had broad industry support, with little to no public opposition.
As for why "broad industry support" is so crucial--it's because Americans care pretty much only about jobs. The media sector has jobs and the internet sector has jobs, and when you can get content owners and tech giants to agree on something, well then from the perspective of a Congressman you're in job-creation wonderland.
It's mind-boggling to hear all these rants about how "democracy is dead" when people here obviously fail to look beyond their own circle of idealistic friends to see what the American electorate is really asking for. E.g. remember Obama and Romney falling over themselves to see who could support coal power more in the last debate? You think it was because of checks written by the coal lobby? Of course not. In 2008, more than half of Obama's money came from donations under $200. Some coal lobby checks aren't going to make a dent in the situation. The real reason the candidates fell over themselves supporting Big Coal is voters. Voters in rural Pennsylvania whose livelihood depends on the coal industry. Hell voters everywhere--even your average American liberal is deeply skeptical of well-established progressive concerns like the environment, and are liable to believe something like "we can't pass measures that raise energy prices in a recession." You think they give a shit about "freedom of information," the "freedom to tinker," etc?
American politics is 90% a referendum on jobs, and has been since the recession of the late 1980's/early 1990's. Big corporations hold themselves out as job creators and creators of economic growth. At least half of voters outright believe that, and even among those that ostensibly don't, they don't disbelieve it all that strongly. That's what creates the corporatism in American politics.
Why does Congress support Verizon's right to lock down their phones over peoples' freedom to tinker with their phones? Because Verizon creates jobs. And while individuals may be annoyed by policies like that, what they are more worried about, indeed deeply afraid of, is any measure that would piss off the job creators.