Well, full disclosure....I'm a Notre Dame fan. However, that's not the reason why I don't like him.
1) His stats are bloated from playing terrible schedules.
Even when he was at Oklahoma his freshman year, he padded his stats against some pretty terrible competition. The only good game he had that season was against Texas, and they weren't that good that year (Sarkisian's first year as HC). At USC, name one top team that the Trojans defeated with him as their QB? Heck, name one top 10 team any of his college teams defeated when he was the starting QB? In his Heisman year, he played one good team twice and they lost both times. Then they lost in the Sugar Bowl to a Group of 5 team (Tulane). His Junior year, he was tearing up some of the crappiest teams in all of college football until a night in South Bend, Indiana, and ND thoroughly exposed his weaknesses to the point where USC won only one game for the remainder of the regular season...where they had to score over 50 points to defeat a very bad Cal team. USC played three teams this past season with a defense ranked in the top 50 at game time....Notre Dame, Utah, and UCLA. All three of them embarrassed Caleb Williams.
2) He's a bit of a head case.
Google his name and the little messages that he likes to paint on his nails. Apparently, it's a little tradition that he's been doing since high school, where he writes "F*ck" and then the opponents name on his nails. While I'm not against using salty language (as I'm sure you've seen), but I'm also not a high profile QB. He is. Doing stuff like not only shows terrible character, but it puts a target on your back. He was told not to do that for the game against Notre Dame this past season...but he did it the year before. The ND players remembered and they beat his ass to a pulp for it. Then there's the NIL drama of college football. He followed his college coach (Lincoln Riley) from Oklahoma to USC but didn't make it official unless he was guaranteed several millions in NIL money. Why does this matter? Well, he already created some drama by saying that he wouldn't sign with a team without getting a share of ownership without understanding that is against the CBA rules. All of this adds up to a drama queen who is going to hold out if the organization doesn't kiss his ass and I don't know about you but the Bears don't need that kind of drama.
3) Is he talented, of course he is...but it's system related. College system related...
Name one QB that Lincoln Riley has developed who went on to tear up the NFL. Sure, he knows how to develop college QB's who can win the Heisman. Baker Mayfield would probably be the best but it took him 6 years and 3 different teams to figure it out. Kyler Murray was exciting to watch for a year or two but aside from cleaning toilets, what's he doing now? Jalen Hurts...most of his development took place at Alabama, not with Riley at Oklahoma. Then there's Spencer Rattler who will go in this year's draft. The dude was a major talent coming out of HS but couldn't get it together until he got out of Riley's system at a different school. Caleb Williams is just another former Lincoln Riley QB who is short (only 6'1") and made the majority of plays outside the pocket. That doesn't work in the NFL. You have to know how to read a defense and I have some serious doubts that Caleb Williams can do that.
4) Do the Bears even have someone who can develop a QB???
Here's the real problem with Caleb Williams. Yes, I know the Seattle OC dude was hired but he's also going to be in Chicago for one year if Eberflus gets fired after this upcoming season. I'm asking a real question here....who on the Bears coaching staff has a track record for developing QB's? He did admirable resurrecting the career of Geno Smith, but what did they win with him? If Geno Smith's minor success the past two seasons is a measure of this dude's success, then the Bears are in for another really long season.
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I don't claim to be Nostradamus, I can't see the future....but I know a turd when I see one. Caleb Williams is a turd. He motivates his opponents to beat him and if there's one rule you should live by, never, ever give your opponents the bulletin board ammunition they need to kick your ass. Caleb Williams does that, a lot. Do you want him writing "Fuck Green Bay" on his nails, and then they body slam his ass into the ground putting him out for the season? I wouldn't want to see that, because then it means the Bears have a Division 2 QB leading the team for the rest of the year (although I do like Tyson Bagent quite a bit, but only as a backup).
Joe Alt on the other hand, is about as sure of a thing as there can be. He's the son of former All-Pro John Alt, he's 6'8" and 320lbs. (not undersized for a LT like our current one) and he dominated whoever was lined up against him since he was a true freshman. Yes, he's a Notre Dame player....yes, I'm a ND fan....but I would want Joe Alt even if you swapped schools with him and Caleb Williams. Taking Joe Alt, with the moves they've made on the OL this offseason, and I'd be more inclined to take a lesser QB like JJ McCarthy, who showed the entire country that you can suck at QB and still win a championship if you have a dominant OL.