1st, Sopa bill wasn't passed in the senate so Sopa bill is useless till now, and it didn't cause anyone's arrest.
2nd
From TorrentFreak, via Digital Music News:
“UMG [Universal Music Group] knows that we are going to compete with them via our own music venture called Megabox.com, a site that will soon allow artists to sell their creations directly to consumers while allowing artists to keep 90 percent of earnings,” said MegaUpload founder Kim dotcom.
“We have a solution called the Megakey that will allow artists to earn income from users who download music for free,” Dotcom said. “Yes that’s right, we will pay artists even for free downloads. The Megakey business model has been tested with over a million users and it works.”
Sources:
http://www.forbes.com/sites/davidthier/2012/01/24/is-this-the-real-reason-why-megaupload-was-shut-down/
http://www.digitalmusicnews.com/permalink/2011/111221airvinyl
To show the power of Sopa, they had to show their muscle but that's not the real reason why they arrested Kimdotcom.
The Sopa bill creators do not care about the rights of digital distribution or anything concerning that matter. They are politician who want to stay in power and make money so megaupload with their new service were a threat to them so they took it out, for now.
We're not regular people, we're the real Internet leechers so it's obvious that that's what's up.