Why Vulkan does not read data from static variables

Suppose we have an Instance class in which VkInstance is created.

class Instance
{
public:
    Instance();
    ~Instance();

    static VkInstance& getInstance() { return instance; }
private:
    static VkInstance instance;
    
    void createInstance();
    
    std::vector<const char*> getRequiredExtensions();
    std::vector<const char*> getRequiredLayers();

    operator const VkInstance& () const { return instance; }
}

In the cpp file, we initialize the variable VkInstance Instance::instance, as well as create VkInstance.

VkInstance Instance::instance;

Instance::Instance() {createInstance();}
void Instance::createInstance(){
    ...code...
    if (vkCreateInstance(&createInfo, nullptr, &instance) != VK_SUCCESS)
        std::cerr << "Failed to create Vulkan Instance" << std::endl;
}

And there is also another class where we connect VkPhysicleDevice.

class PhysicalDevice
{
public:
    PhysicalDevice(const VkInstance& instance) {connectionPhysicleDevice();};
    ~PhysicalDevice() = default;

    VkPhysicalDevice& getPhysiclDevice() { return physicalDevice; };
private:
    VkPhysicalDevice physicalDevice;

    void connectionPhysicalDevice();
    bool deviceVerification(VkPhysicalDevice device);

    operator const VkPhysicalDevice& () const { return physicalDevice; }
};

void connectionPhysicalDevice()
{
    uint32_t deviceCount = 0;
    vkEnumeratePhysicalDevices(Instance::getInstance(), &deviceCount, nullptr);

    if (!deviceCount)
        std::cerr << "Failed to find GPUs with Vulkan support!" << std::endl;

    std::vector<VkPhysicalDevice> device(deviceCount);
    vkEnumeratePhysicalDevices(Instance::getInstance(), &deviceCount, device.data());

    for (const auto& pDevice : device)
        if (deviceVerification(pDevice))                                        //findDevice
        {
            physicalDevice = pDevice;
            break;
        }
    if (physicalDevice == VK_NULL_HANDLE)
        std::cerr << "Failed to find a suitable GPU";
}

main.cpp()

Engine::Instance instance = Engine::Instance();
Engine::PhysicalDevice pDevice();

We will have an error popping up: Failed to find GPUs with Vulkan support! and Failed to find a suitable GPU. But if we change the code as follows.

class Instance
{
public:
    Instance();
    ~Instance();

    VkInstance& getInstance() { return instance; }
private:
    VkInstance instance;
    
    void createInstance();
    
    std::vector<const char*> getRequiredExtensions();
    std::vector<const char*> getRequiredLayers();

    operator const VkInstance& () const { return instance; }
};

class PhysicalDevice
{
public:
    PhysicalDevice(const VkInstance& instance) {connectionPhysicleDevice();};
    ~PhysicalDevice() = default;

    VkPhysicalDevice& getPhysiclDevice() { return physicalDevice; };
private:
    VkPhysicalDevice physicalDevice;

    void connectionPhysicalDevice(const VkInstance& instance);
    bool deviceVerification(VkPhysicalDevice device);

    operator const VkPhysicalDevice& () const { return physicalDevice; }
};

void PhysicalDevice::connectionPhysicalDevice(const VkInstance& instance)
{
    uint32_t deviceCount = 0;
    vkEnumeratePhysicalDevices(instance, &deviceCount, nullptr);

    if (!deviceCount)
        std::cerr << "Failed to find GPUs with Vulkan support!" << std::endl;

    std::vector<VkPhysicalDevice> device(deviceCount);
    vkEnumeratePhysicalDevices(instance, &deviceCount, device.data());

    for (const auto& pDevice : device)
        if (deviceVerification(pDevice))                                                //findDevice
        {
            physicalDevice = pDevice;
            break;
        }

    if (physicalDevice == VK_NULL_HANDLE)
        std::cerr << "Failed to find a suitable GPU";
}

Everything will work correctly for us. And there is such a problem when creating validationLayer and VkDevice. The question is why this happens if getInstance() passes to point to a static variable that is initialized in a single variant, that is, it must pass the actual instance of.