[detaro]

While that plays a role, it's a bit odd to single out Dutch for that - far from the only European country where that is the case.

[DoingIsLearning]

Also a bit glossing over the details if we consider how close Dutch and English are compared with say Slavic languages and English or Latin languages and English.

I remember reading a while back that Old English and Old Frisian would have been mutually understandable. Although in fairness I doubt most Dutch today would follow a conversation in Frisian.