What cartoon says about the reason behind the scandals and corruption of the Harding admin: the Harding admin had no regard/"gave away" their moral responsibility, honor, ethics, etc. (from "Mill End Remnant Sale" sign) so the corruption and scandals reflected this.
Some reasons gov corruption occurs: people are greedy and abuse power (for instance, the greed of Harding's appointees led to them corruptly and illegally selling government property for personal gain).
Did any aspects of the Harding admin contribute to the scandals? The attitude of the Roaring 20s (which emphasized wealth and personal achievements over anything else, so Harding's appointees had no qualms of helping themselves), also the already existing system of corruption in politics at the time (they just joined and worsened it, but didn't start the corruption in Washington).
Fair assessment? Probably, since even though his admin didn't start the corruption, the continued and worsened it for personal gain. They focused on themselves instead of the citizens they were meant to serve.
Should Harding be responsible? He is responsible for appointing them, but their actions are their own and on their own consciences, so he is not responsible for their actions directly (although it's fair he take the blame, since he put them in positions of power that they could abuse and profit from).
What factors might have contributed to this trend: Continued belief that the government doesn't care about normal citizens, rising inflation, continued corruption *just in different forms*, continued government expansion, rising debt.