Top posting has won because major e-mail clients (gmail) made it the default. When you hit reply, they add two newlines at the top and place your cursor there. You really have to go out of your way to bottom post.
Lotus Notes wasn't better in my memory and it was THE corporate email platform back then in the 90's before Microsoft Exchange was a thing then Outlook at the end of the that decade.
They should do what NNTP & SMTP clients did for years: prefix each line with '> ', prepend a line like 'IshKebab writes:' and place the cursor at the end of the quoted material.
Top-posting is pure (albeit minor) evil, a tragedy of the commons and a wastage of space. It's also an unforced error: no-one was clamouring for it, but Outlook and Gmail and Notes foisted it upon the world.