good questions - and your questions are, or could be, actually rhetorical. Yes, they are the validator and thus they control the transactions. It could be as simple as having a Database at the end ... Well I can think of two things:

1- they start by owning all validators, maybe they expect to open validators to other entities at some point in the future. If these entities don't collude together, we could expect some sort of neutrality

2- Marketing - because crypto is coming at an ATH and why not getting some good marketing for free (or almost)

And people mentioning costs, this is not particularly relevant. L2s are extremely cheap by most standards, let alone by Stripe standards which charge horrendous fees.

My questions were not rhetorical. I’m actually interested in the space (fintech, web3, blockchain, etc), but in this space particularly, it’s hard to discern marketing gimmick from use cases where these technologies actually provide real value, so I’m being critical of these announcements while at the same time keeping an open mind.