Your definition of common sense is not really common. Flash, for example, was one of the very early use cases of an ActiveX control. This unsafe technology was supported by Internet Explorer until the end. The IE11 engine is still an installable part of Windows 11. Netscape Navigator plug-ins also were binary code modules. NPAPI was supported by Google Chrome until 2015.

There were warnings from the beginning (both with ActiveX and NPAPI), but for most engineers, getting things done took precedence over trust issues. Youtube, for example, would not have been possible until much later without Flash.