Why don't most products follow a minimalist approach right till the end? Most start ups start like that. But when things begin to fall apart or become better they tend to deviate. While the earlier reason is understandable (because no one likes to fail so they'll do anything to not fail), the second reason seems to me more of an organisational creation than what the users want.

From my understanding as the product becomes popular positions (managerial or product) created need to justify their presence. What do they do? So the breath of fresh air brings in a lot of garbage that may not be required and would be in deviance from the main product idea.

It is debatable that audiences would not accept such ideas that are being brought in, because hey audiences are smart. And they are. But the organisation in order to justify the original wrong decision tends to push their new features (through offers or marketing campaigns). This makes the organisation invested into a wrong direction and security of jobs of the new managers/product people. Win win situation, but lose lose for the organisation and the original product.