I wouldn't call that "obvious".

For starters, it's incomplete. Yes, "some" people think humor itself is offensive. I would wager that there have always been some people like that, since humor itself was invented. How does that relate to what happened to Stack Overflow?

To make your answer complete, you have to connect the remaining dots, and there are multiple ways to do that. Thing is, none of those ways are "obvious".

For example, you could posit that the majority of people find humor offensive today, as opposed to 2014, but I don't see any evidence that's even true, much less obvious.

More likely, you're implying that the majority of people who have influence over Stack Overflow's tone consider the humor itself offensive. If that's obvious to you, it sure isn't to me.