Alright. There is a chance that after touchdown, you might have fallen through the ground causing your aircraft to crash immediately. But this is only a guess.
Here. You will have to share us the replay file to see what exactly happened. Go to the main menu in Infinite Flight, press replay, and find your flight. Press “share replay” and export it to your local cloud. For more information, please visit this topic.
Then, go to https://sharemyinfiniteflight.com/ and try sharing your replay file through this website using the link provided. By linking us your replay file through this website we will be able to access it from here so we could tell you what really happened.