Which brings me to my questions;
1) Is Kane a top draw?
Well firstly the terms "top draw" and "proven draw" tend to be pretty useless, mainly because you'd have to ask every single person who attended/watched an even why they watched and that's never been done. But if your asking if Kane's worth tuning in for, not currently. Even with this new storyline it's really gonna go one of two ways either Kane fights Undertaker or Kane loses to Undertakers attacker and the attacker feuds with Undertaker afterwards. I don't care for either result.
2) Was he ever considered a top draw?
There's that word again, honestly yes in the 90's I tuned in to see Undertaker and Kane and in the early 2000's when it seemed he was getting a push I tuned in to see him lose to HHH every time they met. Since losing the mask not really.
3) Do you agree with my opinon/s above why/why not?
Do I agree that the WWE doesn't see him as marketable? Yes and No, on the one hand it seems sort of stupid to think a guy who was getting great crowd reactions in the early 2000's would've been viewed as unmarketable seeing as so many people wanted to see him go up against HHH and win. On top of that he was second only to the Undertaker in terms of being used as the Alliance crusher.
Similarly when he went up against HHH in the mask for title match I assumed Kane would win as his mask had been a huge part of his character which ended up being ridiculously retconned and it genuinely seemed time for HHH to lose. Nonetheless that didn't happen and instead they turned him heel, de-emphasized his push and made him feud with the Undertaker again before dumping him back in the mid-card as the easily defeatable monster again.
We've had conflicting reports on Kane, some say he didn't want to be pushed and was content with putting over new wrestlers, other reports have indicated that's not the case and that creative just ran out of ideas. I'm not sure if it was marketability, but I think the WWE chose not to push him because his gimmick was essentially intertwined with the Undertaker's, when he was introduced it was "Undertaker's brother Kane" and everything about him involved the Undertaker.
Even when he broke away he was partnered with Paul Bearer, he split from him and was put in lacklustre feuds for his first few years. I think that in the WWE's mind because his first angle's without the Undertaker weren't successful they made the assumption he couldn't be used beyond the mid-card without the Undertaker's involvement. And so even during 02-03 in his best years they scrapped it in favour of turning him heel and sending him back to the Undertaker.
So no, it wasn't money it was the WWE's inability to accept that Kane could do well without the Undertaker and we're seeing it again now, if Mysterio hadn't broken the Undertaker's face this angle wouldn't have run.