No...it's not "strange" at all if you look at it from a business viewpoint and from that perspective it has nothing to do with nor does it matter whether Manziel is better than Kaepernick or not, nor who deserves a chance over the other. You're missing the point here entirely....which is that while a majority of the sports watching or sports knowledgeable public may think Manziel is an idiot or man-child with his hi-jinks, no one really cares enough to make them boycott a team, not watch NFL games or protest against his hiring because of his own stupid stunts. And, many people who are not into sports don't have a clue as to who he is nor do they really care....the majority of Americans know who Kaepernick is and not just for sports reasons. His notoriety to the overall public is as a protestor/anthem kneeler who creates much public & political divisiveness in his wake....there are clear, strong opinions & disagreements about him and people who have & will stop supporting a team (or the NFL as a whole as we have seen in the past) fan-wise & monetarily if he is hired.....as much their right as his is to kneel, protest,etc.
People aren't NOT going to tune in or boycott the NFL if Manziel is hired as a QB somewhere. Not only that, opposed to Manziel who is really a football/sports story, Kaepernick is a political/national story who is discussed by many non-sports media outlets, channels, talk shows and political forums. Manziel might get a mention on Espn/Nfl Network......Kaepernick gets discussed on not only those channels but CNN, Fox, Msnbc, ABC Nightline, etc. as well as a lot of ink in newpapers & magazines , many, if not the majority (hell, the Wall St Journal, the Economist and others did major stories on Kaepernick), having nothing to do with sports.