I think some fans are taking his reaction wrong. I'm sure he's excited about being a Bear, but you better believe he was pissed.
The idea of playing for the 49ers with a coach who has known him since high school, surrounded with a Super Bowl ready roster, after being coached by Ryan Day and John Beck who are both friends of Shanahan and even having a 2nd pro day at the request of the 49ers... it all seemed like fate. He knew he was going to be a 49er... until he wasn't.
Shanahan and Lynch have been running around playing games with the media and with these prospects as well. You better believe Fields is pissed, why do you think he said "theres been too much talking lately" after being drafted?
Fields will love being a Bear, but best believe he's using the draft as motivation. The last time he was that motivated was when Clemson beat OSU two years ago, Ryan Day talked about how much that loss bothered Fields. Well, we all saw what happened the next year.