That's why you shouldn't just go by stats sheets. The difference in Ingram's first 5 games and last 2 games is that the Lakers finally started to run some offense through Ingram rather than just having him play off the ball. I will point out a couple items on the stats.
Firstly, Ingram is not a point guard and he's not an "alpha dog" type of personality. He's not going to have the offense running through him, especially not when he's got guys like Russell, Randle Young and Clarkson on the roster. He's going to have to be able to play off the ball, and his skill set (if legit) should easily allow for that given that his biggest strength is his shooting.
Secondly, in his five games Ingram shot:
1-2 (4 points), 2 reb, 0 ast in 19 mins
2-6 (5 points), 2 reb, 0 ast in 24 mins
3-7 (7 points), 2 reb, 2 ast in 28 mins
3-6 (12 points) 0 reb, 3 ast in 26 mins
7-10 (21 points), 7 reb, 4 ast in 28 mins
There is only one game in that list that I would call a 'good' game, and that is the 5th one. That's despite the fact that he played substantial minutes and took a significant number of shots in all of those games.
One good game among a sea of stinkers does not an "impressive preseason" make.
Ingram's 0.3 turnovers vs. 1.7 turnovers for Brown. Besides his poor shooting, the biggest knock on Brown was his extremely high turnover rate. He's going to have to fix both of those issues to have any hope of being a star.
Turnovers Per Game (TOPG) and Turnover Rate (TOR) for the NBA's top 10 scorers from last season:
Steph Curry - 3.3 TOPG, 12.9% TOR
James Harden - 4.6 TOPG, 15.9% TOR
Kevin Durant - 3.5 TOPG, 13.5% TOR
Demarcus Cousins - 3.8 TOPG, 13.3% TOR
Lebron James - 3.3 TOPG, 13.2% TOR
Damian Lillard - 3.2 TOPG, 12.6% TOR
Anthony Davis - 2.0 TOPG, 8.4% TOR
Russell Westbrook - 4.3 TOPG, 16.8% TOR
DeMar Derozan - 2.2 TOPG, 9.5% TOR
Paul George - 3.3 TOPG, 13.6% TOR
There are only two guys on that list who had a turnover rate under 12.5%, so I don't see any evidence to suggest that a high turnover rate is a hindrance to somebody becoming a star.