Yes, everything you said is correct, ipso facto Microsoft won and was setting the standards at the time.

The competitors still had significant market share and thus their obstinance to follow the leader lead to a large portion of users that had to be catered to by web developers for compatibility due to corporate requirements for access to these market shares.

Thus because these competitors weren't the key demographic, in the context of a developer, they were an additional burden due to the severe lack of uniform standards between major platforms.