Texting while driving is illegal, has been proven to cause distraction and accidents and is a stupid thing to do.
Texting while flying as Captain of an aircraft under VFR or Special VFR or IFR and in marginal weather is crazy, regardless of whether it was a contributory factor at the actual time of the accident or not.
The pilot went against all CRM / ADM learning I have ever seen, he placed undue commercial and operational pressure on himself, there was plenty of opportunity to break this unfortunate chain which he didn't take.