I think they realized that
I think they realized that breaking into the extremely brand loyal modern day truck market was kind of impossible for a brand new electric car company sounded in California. I'm sure the demographics of the people who typically buy pickup trucks don't intersect very much with those who buy Tesla's other vehicles. So I think they realized that breaking into that market was a bit of a lost cause.
Even companies like Honda haven't done well making traditional trucks. I think the actual market that they're going after is the outdoor adventure type. Those who enjoy off-roading hunting or camping.
More the type of people who would buy a Jeep or Subaru, then those who need a serious work truck.
These people are probably more likely to be environmentally conscious as well.