I don’t think he bought any candidates. He might be the man most responsible for Romney’s primary win though, by supporting Gingrich enough to spoil Santorum. I think he had a big part in getting Romney to the top, but that doesn’t mean Romney’s in his pocket. It just means that their opinions more closely coincide on the issues that matter most to Adelson.
We have decided that people ought to be able to use whatever personal resources they want to support their favorite candidates. I think that was a bad idea, but the Supreme Court doesn’t. Either way, Adelson didn’t do anything immoral or underhanded or illegal by pouring money into the primary, and now the general election. He did what any politically minded, motivated person would do, which is to use whatever influence he legally can to get the person he thinks is best for the job elected.