There's a few things going on here, largely driven by the fact that the alien ghost can't communicate directly, it can only influence those who're already moving in the right direction mentally.
The alien ghost has had a considerable amount of time to think about why its craft exploded and how it could have been prevented. When it accidentally discovers Reg's time machine, it convinces him to travel into the past (ancient Greece) where it then waits until it finds someone it can influence sufficiently to write down its story (Coleridge). It then plans to use someone with knowledge of the works of Coleridge (Weeks) to travel further back in time, to share that knowledge with the aliens and hence prevent the accident from ever occurring.
By interrupting Coleridge and convincing him to make his poem shorter, the young girl isn't bored, Reg doesn't feel the need to amuse her and, with the destruction of the time machine, the cycle is broken.
It's less convoluted once you realise that there are two nested time loops, one of which is a bootstrap paradox.