The context here is that the Ark of the Covenant, the symbol of God's presence, was being transported back to Jerusalem after being quite some time in another location. Now, God had given very clear instructions about how the Ark was to be respected and transported. In Numbers 4: 15, for example, we read specific guidelines about how the "holy things" were to be wrapped by the priests appointed for that duty... and an explicit warning that death would be the result if any of the other priests carrying the Ark were to touch those holy things.
Here in 2 Samuel 6, however, it seems that the Ark was being transported by a bunch of willing volunteers..... loaded onto an ox cart like a piece of luggage. So when one of the oxen stumbled and Uzzah reached out to touch the Ark, it was inevitable that he would pay for that with his life. It might seem harsh, but it didn't happen because God was cruel or vindictive.... it was just the way things were, a consequence of disregarding the holiness of God, and the people had been clearly warned of this possibility.
In our modern world, God is often "blamed" for things that happen - things that were not caused by God in any way, but which are a result of mankind's sin and disobedience. Some sicknesses are a consequence of our unhealthy lifestyle... like when people suffer a "burnout" because of their failure to honour God's instructions for Sabbath rest. Some road fatalities happen because people drive too fast, drive when drunk or fail to fasten their seatbelt. It's easy to blame God for things that were actually a consequence of our own poor choices.
When I first discovered that it was going to be difficult to find a new home here in Spain, a number of friends kindly offered me other options - either for the short term or the long term. I appreciated their kindness and care, but when I prayed about the different possibilities, I felt that God clearly told me no; He had made a way for me to have residency in Spain and I wasn't to throw that away.
Later, when I was telling a friend about my decision, she replied in a way that is typically blunt and direct for the people of the nation she comes from. "But, of course," she said, "With your lungs, why on earth would you move to a cold country, spend half the year with bronchitis and maybe end up shortening your lifespan?!!"
Of course, if God had been telling me to move to Switzerland or Germany or Scotland... there would have been protection on my lungs and my health. But I understood her rather bluntly expressed opinion that choosing something that was a "good idea" rather than a "God idea" would not be good for me or for others in the long term.
And so this is what happened to poor Uzzah. No matter how well meaning he probably was, he was doing something that God had never asked him to do.. and he compounded that by doing something that God had expressly forbidden people to do.
