1. Because it isn’t as fragile as some of you say. It won’t go away until it goes away on its own accord - and if anything will kill it, it will be persistent absolute pessimism about the future. That is the only thing that will kill it.
2. Because like other effective memes, it’s “success” is on its own terms, without regard for what is best for the hosts. Just like Republicans don’t advocate for complete capitalism, we aren’t really watching a political battle between bona fide capitalist Republicans and bona fide socialist Democrats. Instead people on the political spectrum support various degrees of a mixed economy. If we let capitalism have its way, the result would be very brutal for most. Ironically, most of the folks that threw their support behind Trump were the “victims” of capitalism’s creative destructive forces that will kill jobs and industries whenever it is slightly more efficient to do so.
As I said, no political party could kill capitalism even if they wanted to.