Mainstream and popular aren't exactly the same, yes the OG series had a huge following of dedicated fans but Star wars as a whole wasn't all that popular overall as an I.P until Disney revitalized it there was what a 10 year gap between revenge of sith and last jedi? Disney is introducing more Starwars lore to the casual fans, no one who wasn't deep into Starwars lore knew who Andor was until Disney released the series, no casaul Starwars enjoyer knew who Thrawn was until Disney introduced him starwars rebels