Cameron was always looking to be a mainstream money-maker and his best movies were all pretty popular, so I don't know about including him in there. I mean yeah, The Terminator was basically an indie movie, but it was made to appeal to a large crowd and his movies after that were all mainstream successes.
I don't know what his motivation was - really, and neither do you.
What I do have, though, is my experience listening to him speak "behind the scenes", during interviews - and his director commentaries. If you listen to him at the time of Terminator and Aliens - you'll hear a very talented and passionate film-maker who cares greatly about his stories and characters. He was always a perfectionist in terms of the technical details - and I'm sure that hasn't changed. He strikes me as a tech-nerd more than anything, and I guess that's what he's chosen to focus on exclusively these days.
But his movies are no longer innovative in any other way than technically - and I greatly miss his strong characterisations and unique plots. He had some great dialogue in the past, and his characters brought new things to the table.
How much he cares about money, I don't know. Seems to me he just wants to be "the big guy" in terms of budget and the spectacle. An ego thing, if I read him correctly. I doubt money was ever the main thing for him.
But somewhere along the way, and in my opinion after Aliens - he became a boring director in terms of character/story/plot and it's gotten steadily worse.
I think he's all about breaking barriers in terms of the spectacle - and I think he greatly enjoys the attention.
Maybe if I cared about such things, I might not be so hard on him - but I just want good sci-fi - and I'm not getting it.