Problems inserting Insert custom canonical value on category page

[mcpacific]

I've created a module to add a custom category attribute (custom canonical URL) to a category page. Here is my block:

<?php

namespace Vendor\Module\Block\Category;

use Magento\Store\Model\Store;

class CanonicalUrl extends \Magento\Catalog\Block\Category\View
{
    /**
     * Core registry
     *
     * @var \Magento\Framework\Registry
     */
    protected $_coreRegistry = null;

    /**
     * Catalog layer
     *
     * @var \Magento\Catalog\Model\Layer
     */
    protected $_catalogLayer;

    /**
     * @var \Magento\Catalog\Helper\Category
     */
    protected $_categoryHelper;

    /**
     * Store manager
     *
     * @var \Magento\Store\Model\StoreManagerInterface
     */
    protected $_storeManager;

    /**
     * @param \Magento\Framework\View\Element\Template\Context $context
     * @param \Magento\Catalog\Model\Layer\Resolver $layerResolver
     * @param \Magento\Framework\Registry $registry
     * @param \Magento\Catalog\Helper\Category $categoryHelper
     * @param \Magento\Store\Model\StoreManagerInterface $storeManager
     * @param array $data
     */
    public function __construct(
        \Magento\Framework\View\Element\Template\Context $context,
        \Magento\Catalog\Model\Layer\Resolver $layerResolver,
        \Magento\Framework\Registry $registry,
        \Magento\Catalog\Helper\Category $categoryHelper,
        \Magento\Store\Model\StoreManagerInterface $storeManager,
        array $data = []
    ) {
        $this->_categoryHelper = $categoryHelper;
        $this->_catalogLayer = $layerResolver->get();
        $this->_coreRegistry = $registry;
        $this->_storeManager = $storeManager;
      $this->_logger = $logger;
        parent::__construct($context, $layerResolver, $registry, $categoryHelper, $data);
    }

    /**
     * @return $this
     */
    protected function _prepareLayout()
    {
        parent::_prepareLayout();
        $this->getLayout()->createBlock(\Magento\Catalog\Block\Breadcrumbs::class);

        $category = $this->getCurrentCategory();
        if ($category) {
            $title = $category->getMetaTitle();
            if ($title) {
                $this->pageConfig->getTitle()->set($title);
            }
            $description = $category->getMetaDescription();
            if ($description) {
                $this->pageConfig->setDescription($description);
            }
            $keywords = $category->getMetaKeywords();
            if ($keywords) {
                $this->pageConfig->setKeywords($keywords);
            }
            if ($this->_categoryHelper->canUseCanonicalTag()) {
                $customCanonicalUrl = trim($category->getCustomCanonicalUrl());
                if ($customCanonicalUrl) {
                    $canonicalUrl = $this->_storeManager->getStore()->getBaseUrl() . $customCanonicalUrl;
                } else {
                    $canonicalUrl = $category->getUrl();
                }

                $this->pageConfig->addRemotePageAsset(
                    $canonicalUrl,
                    'canonical',
                    ['attributes' => ['rel' => 'canonical']]
                );
            }

            $pageMainTitle = $this->getLayout()->getBlock('page.main.title');
            if ($pageMainTitle) {
                $pageMainTitle->setPageTitle($this->getCurrentCategory()->getName());
            }
        }

        return $this;
    }
}

Inside the protected function _prepareLayout() within CanonicalUrl.php it seems $category->getCurrentCategory() seems to work because if I insert $category->getId() immediately after it, the correct Id of the category is retrieved. Also later in the code, $category->getUrl() also correctly retrieves the url of the category.

However, $category->getMetaTitle(), $category->getMetaKeywords(), and $category->getCustomCanonicalUrl() (which should retrieve the attribute 'custom_canonical_url' I added to the Search Engine Optimization group in my module's InstallData.php) all return null, so I'm unable to insert the custom_canonical_url attribute value in the category page.

Why are all these returning null? I assume the reason is the same for all three.