He doubted the financial viability. Not the technical possibility of Heavy. The primary reasons why it made sense after was Ariane and Vulcan delays. You can s

He doubted the financial viability. Not the technical possibility of Heavy. The primary reasons why it made sense after was Ariane and Vulcan delays. You can see that several launches which would have gone on Heavy are now on Falcon thanks to better performance (thanks to planning extra performance for recovery) If Falcon explodes tomorrow no one will blame the engineers