Anecdotal, but I'm convinced I'm not the only person with this experience.
Did Clinton take money (either for herself or for her campaign or for her foundation, it doesn't matter which) from businesses that are canonical symbols of Wall Street money and power? Then she's tainted in the eyes of everybody that is against corporate influence on politics. The contents of the speech isn't particularly important, because it is the influence of money that matters.
Stop looking for traditional political "scandals", and start noticing the anti-corporate-power, anti-globalism revolt that is causing a lot of people to vote "anybody but the usual bribed politicians".
No, but taking a large amount of money does. Even if you believe you aren't taking money for a "bribe" and maintain some level of independence in the actual content of your speech, there is a significant unconscious bias. If you want to get that kind of job again, you might not be as critical of the people paying you.
> The core question is whether the money will influence her policies.
Approach the question from the other side. No for-profit business is going to give large sums of money out without some expectation of a return on that investment. Someone is betting that they will be able to get more money having the ear of a politician than their other investment opportunities.
Regarding corporate influence in politics, I'm a combination of too cynical, too ill-informed and too jaded to offer you any worthwhile thoughts on the matter, and therefore fear I will be wasting your time! It seems to me that entities who generate immense wealth have and will always wield influence in society and the mechanism by which it is brought into order (i.e. politics).