In principle, the market of digital services has the lowest entry threshold one could possibly imagine. Whether you are a billion-dollar enterprise or a private individual; anyone can, at any time, offer their services by merely putting a website online. Same rights for everyone, equal opportunity for participation, the perfect democracy? That is, of course, not the whole story.
Big tech monopolists such as Alphabet/Google, Meta/Facebook, or Amazon effectively control the attention of most users. Their algorithms decide which content you see and how and where you consume it. If the information they provide is biased, this can boost or close businesses and even change election outcomes. If their automated decision-making (ADM) systems operate unfairly, the subjects of those decisions are discriminated. If the platforms they offer are insecure, huge amounts of private data are exposed. If they crawl third-party content and present it as part of their service to eliminate any need for a user to ever leave their sites, those third parties are put out of business.
Of course, all monopolists claim to do no wrong; they simply care for their users' needs and want to provide the best service they possibly can. But even if one believes that and additionally puts aside the fact that good intentions do not necessarily lead to good outcomes, it still holds: With great power comes great need for oversight. (See for example a GI report on the topic: https://gi.de/themen/beitrag/studie-regulierung-von-algorithmischen-entscheidungssystemen)