Agreed, the 49ers treated him like crap.
How so?
Garoppolo was a career backup, stuck behind Brady, until he was traded for a 2nd round pick.
He started five games to finish out that season undefeated and was then rewarded with the biggest contract, in both guaranteed and annual money, at the time.
The next season, he blew out his knee running out of bounds, and the team went nowhere.
His injury history (knee, ankle, thumb, shoulder) has caused him to miss a lot of games for that kind of money.
On paper, his record is good, and he did nearly take SF to two SBs, but as Bills fans will attest, getting there, even four times in a row, is not good enough, and no consolation prize.
SF is not Detroit, Cleveland, or some other hopeless franchise where the SB is a prize in itself, they expect to win it, and the first five times they made it, they won them all, and haven't won one since. Good enough is not good enough.
Time will tell whether Lance is a bust, but the team saw an area where it thought it could improve, and get over that hump, so they took the big bet, with Jimmy being informed every step of the way.
His decision to have shoulder surgery, to the surprise to the team, torpedoed his trade prospects, which would have sent him to a soft landing of his choice, and in the end, it turned out to be the best for everyone involved. He'll get another shot with a SB-contender, can finally prove his doubters wrong (check his standing within the league, not fans), and write his own ticket if he succeeds.
Treated like crap? Ask Baker Mayfield and Jimmy G what that means, and you'll get two very different answers.