Hey!
I'll give you some short answers...

Well, kinda short...
1. But how in the heck did we get here?
One mouthful at a time! While sitting in a chair all day. Enjoying the bounty that we are allowed in this extravagant culture.
2. How did it seem to happen so slowly, but it happened really fast?
For me it didn't happen fast. It happened over decades.
3. How did we LET these lbs creep on?
In my case it was gradual over years. I didn't see it happening in a day-to-day way. Oh, I would gain, and then one day decide to lose some--and do so! And then stop watching, and gain it back plus a little more... and then decide to lose some. And so on.
4. Why did we ignore it?
Because it seemed so gradual, and therefore it seemed like dealing with it could wait. I had more important things to do!
5. Who were we kidding?
Oh, you know who!
6. Where did we go wrong?
I don't think in that way. I think human beings are naturally drawn to tasty, calorie-laden foods because in prehistoric times, these foods were scarce and hard to come by. Now they can be had on any street corner for very little money. So, easy to gain--not so easy to lose. One requires no thinking at all, the other requires discipline, motivation, awareness...
7. What were we thinking?
We weren't, or not clearly. I don't think anyone sets out to become obese! I told myself I had more important things to do than worry about my weight, and therefore I didn't have time to figure out calories and meal plans, and certainly not enough time to exercise! Of course, none of that was true.
Jay