"The Government" is not a entity with "wants" or "needs", it's a collection of people with their own motivations. Motivations that usually end up being about power or money, or a combination, because the people who end up in the government are capitalists.

> why it was the 2nd most important thing to those

I mean, not really? The 2nd amendment includes stuff that they didn't even think of originally when creating the constitution, so just because it was the second amendment that went through, doesn't mean it was "the 2nd most important thing", the most important things are the original articles in the constitution, so the amendments must start ranking at 8th place or something like that, 2nd amendment ends up being the 9th most important thing if we were to rank things like you did, but honestly.