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That would take years.

Remember OpenOffice.org? That is still getting ~100,000 downloads a day in April this year [1]. That's after all the Linux distros moved to LibreOffice for years. Forks work for moving development, but not necessarily for moving users.

[1]: https://lwn.net/Articles/729460/

MySQL and MariaDB are another example, if you need one. :)

How did those users come to learn about VLC Player

A computer-savvy acquaintance installed it for them once upon a time.

It seems you never had to deal with such users, they talk about that orange thing or the traffic cone. Which should be more than enough to explain why they would not migrate.