They don't seem to have ever blamed Leopold, likely taking the view it was a horrific freak accident. Given what they wrote themselves:
''When we, Queen Astrid's parents, accompanied our daughter, as your Kings wife, to her new home, nearly nine years ago; her father said that we could leave our beloved child to her husband and to the Belgium people, with joy and entire confidence.
This confidence has never for a single moment been betrayed. Much more, from the moment our dear Astrid set foot on Belgium soil, the whole nation has surrounded her with a love which grew in strength and warmth with the years passed.
Nobody better than us, her parents, know that the people's love and confidence in her desire to give herself entirely to her new country, gave her strength and made her happiness as wife and mother complete, and nobody knows better than us that this happiness remained clear and lasting.
Nobody will wonder therefore that we should consider it a dear duty to bring the Belgian people our deep and heartful thanks for the love which they always surrounded our beloved daughter.
Your dead queen from her Nordic home, loved Belgium. The love of the nation found an echo in her warm young heart. Great is our sorrow, but greater still is our sympathy for your young king and his little children, and our gratitude to him for everything he was for her, and for the great happiness he gave her.
Carl & Ingeborg (signatures)''
This can also be seen as when he remarried they simply said he was a young man and it was normal that he shouldn't be alone for the rest of his life. If they had been angry at Leopold for that, or anything else, they could have easily just kept silent.
What I'm curious about is if being first cousins once removed themselves, they were as opposed to Märtha marrying her first cousin Olav as Haakon and Maud apparently were?