Gun nuts believe their position is popular. It isn't. They have (have had) intensity on their side for two reasons. One reason is that "gun nuts" are, well, nuts, and they are single issue voters about it. There isn't an equivalent voter opposition. The second is that there isn't an equivalent opposition from electeds. When Democrats do propose gun measures, they're...ant steps. Maybe they're good policies, but even supporters recognize that they're not likely to do much about the basic problem of people killing themselves and each other because it's too damn easy to buy a gun. One side has "give us all the guns all the time fuck you libturds" and the other side has "maybe we should ban bump stocks?". You can't really build a big movement around that.
The outcome of Heller (individual right in 2nd amendment) was supposed to open the door to sensible gun regulation. Fine, it's a right, so we can't take away all your guns, but that doesn't mean we can't have some reasonable regulations. That was a stupid view because that isn't how politics works (nor is it how conservative judges are likely to see Heller). But little things like "constitutionality as interpreted by the Supremos" never stop conservative activists.