Lots of comments on trades made in the last few years, but from the Herschel Walker mega-trade to 2013, the were very, very few in-season NFL trades. The last few years have been an aberration from the norm during that time period. So have a lot of other traditional rarities. Missed PATs, going for 2, going for it on 4th down.
I think the norm is changing overall in the league. Even the types of player for picks and player for player deals during the off-season seem to have increased over the last handful of years (seemingly I did not look it up). the core of talent acquisition is the draft, but teams have been more aggressive in using other ways to get players.