In what ways is it possible for alternative forms of music to achieve chart success?

Not sure exactly. Been wondering this myself for a long time. Thought it was pretty amazing in the early 90's when the heavier stuff started showing up and having chart success - Soundgarden, Nirvana, it was about this point that I started seeing less and less "pop" junk on the charts, and a new focus on what was once considered "alternative" or "college radio" sound becoming more mainstream. Same for hip hop. It's just dominating nearly every genre it seems now, you have crossover between rock and hip hop, country and hip hop, etc. People's tastes vary, and the "alternative" sound now (which could include hip hop in some respects) is just what everyone is used to now.

Was this what you were getting at? An opinion of how "alternative" is having so much success?

first, alternative is a broad term. where do you draw the lines? to me, alternative is anything that's not mainstream, but one can argue that Radiohead, for example, is alternative, which i do no perceive it to be.

NIN reached success, although not on the charts. the ultimate secret is to be in the right place at the right time. if the beatles were forming this very day and if the white album was to come out in a year, do you think anyone would care? no. they'd end up on mp3.com, waiting for someone to hopefully offer them a project to work on.