I'm sure that many if not all of those 55 against votes were not based on a belief that "he didn't do anything wrong", but rather that the offense was not of a grave enough magnitude to merit removal from office.
For a little context, if a normal citizen was caught lying under oath with the same evidence, most District Attourneys wouldn't even bother to prosecute the case. I've seen footage of President Bush jaywalking. That's breaking the law, I suppose he should be impeached and removed from office for jaywalking. Granted, lying about one's personal life under oath is worse than jaywalking, but it is closer to that end of the spectrum than it is to say murder or treason. Lying to Congress about the reasons for war, when it is Congress' authority and responsibility to declare war, is further towards the bad end of the spectrum, IMO, but perhaps still not aggregious enough to merit removal from office. If the Democrats had the numbers required in the House, don't think for a second they wouldn't have impeached Bush already.
By voting on the side of sanity rather than with the neocon lynch mob, the Republican Senators who did not follow the party line probably earned a few more years of relatively fillibuster free Senate activity (goodwill which appears to have dissipated as of late). The problem with childish partisan politics in the Senate is that without a fillibuster proof majority, a single pissed off senator can potentially shut down Congress indefinitely. That traditionally forces the Senators to be a little more respectful of each other and more amenable to logical compromises.