Why there is so much difference between these methods of creating string

I was going through a site to benchmark the small functions and methods in c++ for the purpose of optimization and performance and I found some results on strings that I am not able to figure out why. Link http://quick-bench.com/mNexo7ae75tYgt8HYoB17HEHgKc for the benchmark code.

static void StringCreation(benchmark::State& state) {
  // Code inside this loop is measured repeatedly
  for (auto _ : state) {
    std::string created_string("hello");
    // Make sure the variable is not optimized away by compiler
    benchmark::DoNotOptimize(created_string);
  }
}
// Register the function as a benchmark
BENCHMARK(StringCreation);

static void StringCreationMove(benchmark::State& state) {
  // Code inside this loop is measured repeatedly
  std::string x = "hello";
  for (auto _ : state) {
    std::string created_string_move(std::move(x));
    // Make sure the variable is not optimized away by compiler
    benchmark::DoNotOptimize(created_string_move);
  }
}
// Register the function as a benchmark
BENCHMARK(StringCreationMove);

static void StringCopy(benchmark::State& state) {
  // Code before the loop is not measured
  std::string x = "hello";
  for (auto _ : state) {
    std::string copy(x.c_str());
    benchmark::DoNotOptimize(copy);
  }
}
BENCHMARK(StringCopy);

static void StringCopyByChar(benchmark::State& state) {
  // Code before the loop is not measured
  const char* x = "hello";
  for (auto _ : state) {
    std::string copyChar(x);
    benchmark::DoNotOptimize(copyChar);
  }
}
BENCHMARK(StringCopyByChar);

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