To install CorelDRAW 2020 after uninstalling CorelDRAW 2025, you must also uninstall the VBA for Autodesk AutoCAD 2025 component.
There is a known issue related to different versions of Microsoft Visual Basic for Applications ("VBA") interfering with Windows application installations.
Please have a look at this knowledge base article "How to disable Visual Basic for Application (VBA) during CorelDRAW Graphics Suite Installation" that explains the problem and a workaround for installing CorelDRAW Graphics Suite, specifically versions prior to 2025: https://kb.corel.com/129863