The first is in its substantial backing. The scheduled 2x fork is the result of the "New York Agreement" between an impressive collection of major industry players including miners, wallets, exchanges and payment processors.
At its inception, the agreement claimed the participation of 58 companies located in 22 countries including many of the largest in the ecosystem, and 83.28% of miner hashing power. This represented the most significant push for any hard fork to increase the block size by far.
Segwit2x breaks this trend by declining to enact replay protection and also failing to publicly seek and build wider community support for the adoption of the software.
Firstly, the doubling of the block size that Segwit 2x solely exists to implement has been rejected by the vast majority of the open-source development community on technical grounds, and as such, is not being merged into Bitcoin Core, the most widely used and supported bitcoin client by far.
Exchanges have also largely recognized "legacy" bitcoin, and after the fork, that Segwit2x coins will be treated as separate units of value. This is opposed to Segwit2x's original intention and goal, which was to seamlessly replace the current bitcoin protocol and the corresponding unit of value.
companies are ultimately profit-oriented and will live or die with the ecosystem, and it is doubtful that the repercussions of a deeply contentious fork without replay protection is lost on the majority of them. That this is being risked for a simple block size increase makes it an even more unsavory deal. To put it simply, circumstances have changed dramatically since the participating companies agreed to what then likely seemed like a safe and straightforward commitment.
