Well, to be fair, I don't think Beiber and Gaga were good examples to use as pop stars gone country. Justin asked Rascal Flatts to perform his song "That Should Be Me" with him, but that's as far as he's stepped in country. Gaga always does remixes of her songs- as they always do in pop music. It's not surprising in the least to see her do this. Just because someone wants to experiment with an artist from another genre doesn't mean they want to be in country music.
I think the article was talking about people who are not experimenting, but trying to simply make a profit & start over in country music.
Jessica Simpson, Darius Rucker, Jewel, Michelle Branch, Kid Rock and Bon Jovi have all tried to "make it" in country music. Even Kelly Clarkson has done a few country songs, after her duet with Reba, and not being as successful as she once was in the pop world.
Thankfully, country fans are quick & smart enough to decide who they do/don't want in country music very quickly. I think the flop success stories of by so many pop artists who have tried to go country proves that it's NOT as easy to get into country music and it seems, and it doesn't mean people will accept you as a genuine country artist just because you couldn't make it in pop.