The Bitcoin ledger is a single global truth. Mutually untrusting nodes agree on this one truth, with no central authority to call the shots or enforce rules.
and yet a central group did become an authority in 2017 by dictating a bip91 lag that would mandate a split to ensure that those loyal to the group enforced a new ruleset.
it was not unified agreement and then activation. it was separating oppositions to enforce a change
without bip91 mandatory split bit4. the segwit bit1 would have remained at ~45% from july 23rd to august 24th
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it cant be a united consensus. if there is methods to mandate changes by certain groups of people