It was a company founded with a purpose and recent actions threaten that purpose - that's easily characterized as a betrayal.
Either way, there's no slippery slope here. I do believe already that most business owners are acting immorally in the pursuit of personal gain. I don't believe "wanting to get richer than other people" is actually a defensible motivation for actions that either worsen the experience of other people or prevent others from getting a share of that wealth.
edit: the content of the comment I'm replying to completely changed while I was writing my reply, but I'm just going to leave this here.
> It seems doubtful whether any employee genuinely excluded the possibility of the owner eventually leaving when they signed up. It's not some rare or obscure edge case.
Of course they know it's a possibility, but surely most hoped the temptation would be resisted. Again, the whole point of the platform was to focus on artists first, and fans second, and growth somewhere behind that. But all that is only talk without contractual obligations, and so we see the company sold out and gutted because they can.