Another advantage is that they are inherently available across OSes, usually across different browsers (but we know what it takes.)
Finally, they used to be much more easy to develop.
Tldr: larger audience, less costs.
The true definition of a full stack developer in those days would make today's definition of full stack faint.
You had to know how to setup hardware with an os with your software and databases, often having to run your gear in a datacentre yourself that you had to figure out your own redundancy for, all for the opportunity to code something to try out. Being equally competent in hardware, networking, administration, scaling and developing a web app was kind of fun. Now those jobs are cut into many jobs.
Activex was what flash tried to be.. The promise of Java of using one codebase everywhere.
Seeing webassembly is exciting.
people really thought activex was brilliant...until security became an issue. i can remember when the tide changed.
anyway, fair points otherwise. cheers.