Both authors started writing right after and as a result of WW2.

As terrifying as all this is, we encounter it in a childlike world where, however bad things get, mother is able to make them right. ‘If only we can get home to mamma before it comes, nothing can happen,’ Moomintroll says anxiously when he learns the time that the comet will hit. ‘She will know what to do.’
The strain this put on the family is transformed into Moominpappa’s absence. He has ‘[taken] off with the Hattifatteners’, ‘who are forever wandering restlessly from place to place in their aimless quest for nobody knows what’. Moominpappa later quietly omits his infatuation with this strange, mindless crowd when he writes the story of his life, which was the approach taken by many Finnish supporters of Nazi Germany. When Moominpappa’s memoirs are complete, there is nothing in them at all about his wayward years with the Hattifatteners, much to Snufkin’s puzzlement.

I’m also not sure whether that is a case of blue curtains or not:

It is in their depiction of gender and sexual fluidity that the stories are most radical. Jansson herself had relationships with both men and women before finally settling, as she put it, on ‘the spook side’, with a female partner, the graphic designer Tuulikki Pietilä. […] Thingumy and Bob have a secret language and hide the King’s Ruby, which symbolises their love, in a suitcase. But the Groke, who represents the forces of repression and negativity, wants to deprive them of it. In the parody court that the Moomins hold, the Groke’s legal right to the ruby is contrasted with Thingumy and Bob’s moral one. In Moominland Midwinter (1957), Jansson brought Pietilä into the book as the character Too-Ticky; though referred to as ‘she’, Too-Ticky dresses in trousers and Breton tops, with short hair, a beret, and a knife on her belt.