You don't strictly need mass consensus for a softfork. Taproot is a softfork, which means a tightening of the rules. There are basically a set of placeholder s

You don't strictly need mass consensus for a softfork. Taproot is a softfork, which means a tightening of the rules. There are basically a set of placeholder script types, that are currently undefined by the network ruleset. By being undefined, you can basically add whatever garbage you want, and it will technically be valid. So, blocks that are mined now with taproot transactions are still considered valid by nodes and miners that haven't upgraded or don't support the change. Their nodes just see these transactions as unintelligible garbage, but still permissible. However, the risk these nodes take on by not upgrading support, is that they might receive a block, assume it's valid even though there are transactions they don't understand, but in fact are invalid taproot transactions and rejected by the upgraded network. This is a much greater concern for miners than regular nodes, because miners have severe economic risks associated with incorrectly assuming an invalid block is valid, whereas non mining nodes don't have as great of a risk, because they generally wait for several confirmed blocks before assuming their transactions were confirmed.