It's the right decision: Android is mostly open source and works well. Not to mention that in real life, right now, people need access to certain apps as a firm requirement.

Have you seen the attempts of past "Linux phones"? Usability, performance and usually battery life were horrible and progress was also slow.

There have been comments about the race to support recent phones. I hope that Fairphone will looked at as a target device. It would be a good cultural fit and they don't have a yearly device cycle which should also help.