Lampard was just a temporary manager for Chelsea and he wasn't expected to do bigger things much. Because Chelsea tried Lampard as a permanent manager before as well but it didn't work out well at all as you remember. Lampard just doesn't have it in himself. He couldn't do well at Everton either so I think it would be better for his career to do a different job then being a manager.

Pochettino is a decent manager and I feel myself confident about him to do much better than Lampard. If Chelsea build their lineup in a solid way I think they will be competitive for top 4 again in a short time.