Definitely terrorism, and let's not forget that he set off high powered explosives in front of a venue related to the President-Elect of the United States and one of the President-Elect's close associates. That, in itself, should qualify as a terrorist act, regardless of the offender's political or other views.
We also don't know if he planned to carry out a plan to mow down people in Las Vegas on New Year's day or New Year's eve, similar to the terrorism in New Orleans. So far the authorities are saying it is unlikely, but it is still under investigation. Did he arrive too late to do what his original plan was and so just go to step 2 and find a place to commit suicide and set off the explosives? Did the trip take him longer than he thought it would, given the need to keep stopping to re-charge the cybertruck? Or did he have second thoughts about driving on the strip and mowing down people in Las Vegas?
I think that ultimately he was going to commit suicide, but until the matter is thoroughly investigated it is possible that he planned to take out others with him. We just don't know yet.
Was he partially radicalized overseas before he returned for the holidays?
Still too early to know, IMO, let the FBI and others investigate which will take time.