There are always two sides to the story. I won't blame NZ government to cancel the tour if they felt that players were at risk of getting attacked. Tank, 4K security, etc won't be enough to keep the tour going on if the government got some credible threat. Tank, 4K security etc may have been enough to convince the team to come, but no team is going to stay in Pakistan if they get a credible threat.
Now there is another side of the story here which you may not realize. Cricket fans in Pakistan have endured 10-15 years of not seeing many international teams. The ground situation was worse back then and based on what I read in PP, the situation has improved a lot. Now, the situation is surely not as safe as many other countries, but definitely much better. Pakistan has taken many steps to get small tours, getting Zim, BD etc. NZ pulling out creates big reputational damage for Pakistan when it comes to getting cricket back and assuring other teams about security. Sure, it is not really NZ government concern, but Pakistan fans will surely be frustrated with the situation after making so much progress and now the situation has taken many steps back.