The ex and her idiot will be fine. They will live a decently comfortable life. Sure, they are placed far, far away from things like career advancements and luxury, but they both live a comfortable and happy life.
HAHAHA, NO!
All that happened at first, but they lost it all because both of them are idiots. The ex, so used to luxurious life, overspends like crazy. The idiot, realizing that he's stuck on a dead-end branch in a dead-end position, starts to act like a jerkass and ended up not at all satisfied by his current life. They eventually got a really, really HORRIBLE breakup.
The ex eventually tried dungeon diving to fund her lifestyle (if "that idiot" can do it, she can do it too) only to got tangled with the worst possible situation... until the MC (or his disciples? I forgot) helped her. She eventually found herself meeting the MC and his disciples and finally, genuinely apologizes.
Forgot what happened to the idiot, but let's just say things are not at all looking good for him.