Depressed cat because I moved away with the other cat

I got my cat in 2020 (Tuxedo), Tuxedo is my cat.
In 2023 my mother adopted a Tabby cat, tabby cat became my mother’s cat.
Tabby has always been the one to be the most playful and more expressive (attached) to the ones he trusts and loves (aka: my mother, my cat, & me as human replacement for his main human)
I moved away and I had worries that her cat would get absolutely depressed, I had fears mine was going to be sad but not so much because sometimes I felt that my cat felt like he couldn’t go outside my room because the other cat was always bothering him chasing him (trying to play 25/8)
Surprisingly I was right. My cat adapted quick to its new environment but my mother’s cat is now always hiding under the bed, she says he eats but is not like before (he’s those ones that is always begging for food as if he’s been starving, big back boi) What can we do to make my mother’s cat happy or less sad? I’ve heard horror stories of cats grieving another that they die not too long after the other… mine hasn’t died but Tabby doesn’t know that
I live an hour away now, I fear that taking my tuxedo to visit Tabby will make tabby happy for a little and then bit HARD again.
My mother works 9+ hours Monday-Friday(sometimes Saturdays too). So when neither me or my mother were home, Tuxedo was always “there” for Tabby.
Tuxedo knew life before Tabby.
Tabby never knew life without tuxedo.
I really worry, I cry a lot thinking about it, what can I do that’s not taking my cat on constant trips back and that isn’t adopting another cat?