With Axel playing CB Villa have conceded 19 goals in 12 games in the Championship.
When Axel not on the pitch, Villa have conceded 15 goals in 10 games.
With Axel playing RB Villa have conceded 11 goals in 6 games.
I have no idea how many of those goals, Axel was partly at fault for. However, I do know Villa's defensive record is currently the 3rd worst in the Championship, though there are a couple of teams who have played a game less, who might alter the position slightly.
At the time Lindelof was signed, it did seem a strange decision given that his skill-set seemed similar to that of Tuanzebe. Having said that, at this point in time there is a huge difference in terms of their respective experience. One has played in the World Cup as well as quite a few CL games for Benfica and United, and PL experience.