ok but like ??? wh y did the galra have red lion though?? clearly black is the one zarkon is hung up on so theres literally no reason why he would prioritize capturing red over black. but even still red seems to be the most “lively” of all the lions. i cant see it just being complacent to sit there and let the galra mess with it for 10,000 years??
anyway i think the old red paladin was probably still loyal to the galra or something and thats why red was alright with staying with them and waiting around until someone better came along. Allura does try telling her dad to form voltron, which suggests they had a pilot for every lion, but zarkon was the original black paladin so its not totally out of the question. also she mentions there being some dark past associated with pretty much all the paladins so. theres that. but also, red seems to be the most picky about their paladin
so maybe red was just so attached to its pilot that after they died/got captured it just like?? shut down?? it couldve also been completely shot of quintessence or something i guess, maybe having lost it all in a last stand for the red paladin.