Because the chance that it was a action controlled by the Russian government gets significantly lower if some people of russian ethnicity did it where the Russian politics don't have any control over. Everyone hated Clinton, I hated her since she told that there was nothing wrong about Lybia. I'm not a russian citizen nor east European, but I was glad that Trump got elected. Murica is doing like Russians stole all the voting papers and replaced them with trumps, but it takes more than a bit of online propaganda to elect a president. Btw. Something the US government has a long tradition in doing. Don't get me wrong, it's definitely not okay to interfere in any election in this world but for God's sake, deal with it. Now give me all the downvotes, people that voted for Trump because of Russians. LOL.