<?php
namespace Vendor\Namespace\Setup;

use Magento\Cms\Model\Block as CmsBlock;
use Magento\Cms\Model\BlockRepository;
use Magento\Cms\Model\BlockFactory;
use Magento\Framework\Exception\NoSuchEntityException;
use Magento\Framework\Setup\ModuleContextInterface;
use Magento\Framework\Setup\ModuleDataSetupInterface;
use Magento\Framework\Setup\UpgradeDataInterface;

/**
 * Class UpgradeData
 */
class UpgradeData implements UpgradeDataInterface
{
    /**
     * @var BlockFactory
     */
    private $blockFactory;

    /**
     * @var BlockRepository
     */
    private $blockRepository;

    /**
     * UpgradeData constructor.
     *
     * @param BlockFactory    $blockFactory
     * @param BlockRepository $blockRepository
     */
    public function __construct(
        BlockFactory $blockFactory,
        BlockRepository $blockRepository
    ) {
        $this->blockFactory = $blockFactory;
        $this->blockRepository = $blockRepository;
    }

    /**
     * Upgrades data for a module
     *
     * @param ModuleDataSetupInterface $setup
     * @param ModuleContextInterface   $context
     *
     * @return void
     * @throws \Exception
     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
     */
    public function upgrade(ModuleDataSetupInterface $setup, ModuleContextInterface $context)
    {
        if (version_compare($context->getVersion(), '1.0.1', '<')) {
            $cmsBlocksData = [
                [
                    'title'      => 'Title',
                    'identifier' => 'cms_block_identifier',
                    'content'    => '<p>Some content</p>',
                    'is_active'  => CmsBlock::STATUS_ENABLED,
                    'stores'     => 0
                ],
                [
                    'title'      => 'Title 2',
                    'identifier' => 'cms_block_identifier_second',
                    'content'    => '<p>Some content</p>',
                    'is_active'  => CmsBlock::STATUS_ENABLED,
                    'stores'     => 0
                ]
            ];

            foreach ($cmsBlocksData as $cmsBlockData) {
                /** @var CmsBlock $block */
                try {
                    $this->blockRepository->getById($cmsBlockData['identifier']);
                } catch (NoSuchEntityException $e) {
                    $block = $this->blockFactory->create();
                    $block->setData($cmsBlockData);
                    $this->blockRepository->save($block);
                }

            }
        }
    }
}

<?php
namespace Vendor\Namespace\Setup;

use Magento\Cms\Model\Block as CmsBlock;
use Magento\Cms\Model\BlockRepository;
use Magento\Cms\Model\BlockFactory;
use Magento\Framework\Exception\NoSuchEntityException;
use Magento\Framework\Setup\ModuleContextInterface;
use Magento\Framework\Setup\ModuleDataSetupInterface;
use Magento\Framework\Setup\UpgradeDataInterface;
use Magento\Store\Model\Store;

/**
 * Class UpgradeData
 */
class UpgradeData implements UpgradeDataInterface
{
    /**
     * @var BlockFactory
     */
    private $blockFactory;

    /**
     * @var BlockRepository
     */
    private $blockRepository;

    /**
     * UpgradeData constructor.
     *
     * @param BlockFactory    $blockFactory
     * @param BlockRepository $blockRepository
     */
    public function __construct(
        BlockFactory $blockFactory,
        BlockRepository $blockRepository
    ) {
        $this->blockFactory = $blockFactory;
        $this->blockRepository = $blockRepository;
    }

    /**
     * Upgrades data for a module
     *
     * @param ModuleDataSetupInterface $setup
     * @param ModuleContextInterface   $context
     *
     * @return void
     * @throws \Exception
     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
     */
    public function upgrade(ModuleDataSetupInterface $setup, ModuleContextInterface $context)
    {
        if (version_compare($context->getVersion(), '1.0.1', '<')) {
            $cmsBlocksData = [
                [
                    'title'      => 'Title',
                    'identifier' => 'cms_block_identifier',
                    'content'    => '<p>Some content</p>',
                    'is_active'  => CmsBlock::STATUS_ENABLED,
                    'stores'     => Store::DEFAULT_STORE_ID
                ],
                [
                    'title'      => 'Title 2',
                    'identifier' => 'cms_block_identifier_second',
                    'content'    => '<p>Some content</p>',
                    'is_active'  => CmsBlock::STATUS_ENABLED,
                    'stores'     => Store::DEFAULT_STORE_ID
                ]
            ];

            foreach ($cmsBlocksData as $cmsBlockData) {
                /** @var CmsBlock $block */
                try {
                    $this->blockRepository->getById($cmsBlockData['identifier']);
                } catch (NoSuchEntityException $e) {
                    $block = $this->blockFactory->create();
                    $block->setData($cmsBlockData);
                    $this->blockRepository->save($block);
                }

            }
        }
    }
}