For small to midsize businesses Microsoft Windows based systems remain dominant. Windows continues to be the operating system most widely used on desktops and laptops. And Microsoft Office remains the most widely used work office suite. So it’s no surprise that Windows system remain the top target for ransomware, too.
Here’s a good read that tells you why it’s so important to keep your systems current: https://silicon.co.nz/wp-content/uploads/2019/11/Ransomware-and-Office-365-eBook.pdf