Anyone explain this housefly behavior?

Our garbage collectors used to dump the whole bin in the truck, and then one day just started pulling the trash bags out and throwing them, manually, into the compactor. So this would often leave items in the very bottom of the bin. We had a bit of a…let’s just call it a “baby fly” problem, which I fought with bleach and lysol. (not sure if this has anything to do anything, but just giving a little background, in case)

So the other day, I went to roll the trash bin out to the curb and noticed there were about 6 adult flies on it…dead, but lifelike…

Then on the other trash can, same deal. And not like a dead fly that’s been between the window and the screen for 6 months has been preserved, like these things were standing on the side of it, still stuck to it.

They are also on the wall…dead.

Here’s a wide:
And a tight:

Look pretty live except for the posturing of the wings.

I guessed that maybe they slept there one cold night and then were killed by the cold and their feet adhesive was employed? But when I noticed it, we’d only had one cooler night, maybe down to 40…not even freezing.

Either way, not the kind of curb appeal we were going for.