The article discussed here suggests it was related to the crisis:
The common element appears to be the global financial crisis, which affected economic activity and governments’ capacity to finance continued health care spending growth.
On the other hand, the author notes that it started before the crisis:
As I’ve argued in the past (here and here), U.S. health care spending seemed to slow down in the mid-2000s, well before any cost-constraining measures of the 2010 legislation could take effect. In addition, the slowdown in health care costss has been international, which suggests that changes in U.S. law are not the driving factor.
So either way, the slowdown may have multiple causes, and we have some reason to believe ACA wasn’t as important. Frankly, it’s only just kicking in, so listing it as a cause is silly (case in point).