What's the other one besides Bitcoin? Ripple, Ethereum, Litecoin or Dogecoin? These are one of the oldest coins out there, so it is not surprising that they have more network effect.
Did Bitcoin foundation made all those deals that Bitcoin is more accepted than others? No. Obviously the communities are decreasing during the bear market, there was lot of companies who accepted Bitcoin too before the fees went nuts, they discontinued accepting Bitcoin. Many haven't still returned even that fees have gone down and Lightning has become available, many still don't even use native-SegWit (P2WPKH) or pay-to-script-hash (P2SH), but old pay-to-pubkey-hash (P2PKH), which takes longer to be confirmed (I could be wrong about that, but SegWit transactions should be possible to validate faster).
Cryptocurrency companies are not like regular companies where partnerships only happen when deals are made. Cryptocurrencies are open-source, so everybody can become a merchant, you don't need to ask permision for that. If you like the old adoptions-by-deals approach then maybe Ripple is your kind of coin.
Now, during the bear market, it is time to build all those intergrations and those who are ready for next bull-run, benefit from that more.