It was 100% reckless. If it wasn't you'd see it happen a lot more.
Fitzpatrick chose to make a play where injury had a higher probability in lieu of that player scoring a TD.
It was a conscious decision that had an expected outcome. If he played clean football and tackled soundly and Chubb got injured that would have been a much lower than expected outcome. It's just interesting that the guy is being defended for diving at a guys knees in the name of not allowing the TD when the outcome of what would happen was pretty certain injury.
Again, ask yourself, how often does this type of thing happen?
The "play" he chose to "make," probably happens more than you would think. The RB is just usually better able to avoid the contact directly to the knee. A half a second sooner or later and the outcome is likely different. Unfortunately, multiple people were making near instantaneous decisions at that moment. They all came together in a horrific way.