I think block size war is a contributing factor. If we account for all the contentious hard forks between 2015 and 2018, we will can trace vast majority to disagreement, particularly the case of block size limit.
To answer the question "What happened differently" I will simply say the Bitcoin ecosystem matured. The main tensions that caused forks have cooled off, and Bitcoin’s development has shifted toward incremental, backward-compatible upgrades, reducing the threat of contentious splits.
Disagreement is part of manipulation game if you notice what happened with Taproot upgrade in the last market cycle too. It was less severe than Segwit upgrade in 2017 but basically market manipulation game is the same.
If upgrade on Bitcoin protocol can be voted, aggreed easily and in short time, it will not cause any uncertainty in the market and people will not feel either panic or hyped. Market makers know how to trigger unstable emotion and weak psychology of market participants in order to accumulate cheap coins before they boost the price up and take profit in distribution phase.
During manipulation time, there are scammers who take advantage of chaotic time in order to create forks and steal bitcoins from unknowledgeable bitcoin owners.