Cant blockchain ledgers colude against users?

Hello,

I’m reading Chicago’s Fed paper on blockchain and trying to understand the safety characteristics it offers.

Everybody says that one feature that stands out is the safety of the DLT, but I was thinking (i know I don’t have all the details of how the network works), can’t there be a collusion between the ledger operators in detriment of the users? Can this be possible?

Given there is no authority regulating the DLT, is it really that safe that this operators are the ones that approve or disapprove a financial transaction? and, isn’t there a sort of asymmetric information where this operators of the DLT might have some sort of conflict of interest against a particular transaction and collude together and not accept it? (i.e. a payment of some sort that comes from an unfriendly social transaction).

I’d like to know your thoughts.

I’m not talking about other types of networks, but Bitcoin in specific. Is it really that safe for money transactions that come from different activities?