Did you already get the coroners report?
Texting alone or nodding off could either do this
So could checking a side view mirrors at the wrong time or any number of things that led to the truck driver being distracted a bit too long when he should have been paying attention...
Not paying attention is probably the #1 cause of collisions. The #2 cause is drivers who lack driving skills and or inexperienced drivers who simply can’t drive worth a s**t.