According to the founders and early engineers on their podcast - no, they tried to fairly evaluate all the oses and were willing to go with other options.

Practically speaking, its hard to do it completely objectively and the in-house expertise probably colored the decision.

Tried to, sure, but when you evaluate other products strictly against the criteria under which you built your own version, you know what the conclusion will be. Never mind that you are carrying your blind spots with you. I would say that there was an attempt to evaluate other products, but not so much an attempt to be objective in that evaluation.

In general, being on your own private tech island is a tough thing to do, but many engineers would rather do that than swallow their pride.