[sayurichick]

miners mine because they want bitcoin.

you end up on a diff chain if the bitcoin software you run has different consensus rules. Nobody would do this because there is no incentive to be on a brand new network by yourself even if you managed to have enough hash power to survive the difficulty algorithm.

even if you do mine a lot of bitcoinXfork, good luck trading/selling it.

[jzl]

But even assuming cooperation how does a decentralized system settle on agreement about the next block with so many miners potentially in contention? What is the average time interval between block discovery?

LET ME GOOGLE THAT FOR ME: Ok, this chart shows that the average time is around 8 minutes. I guess that makes sense as being enough time for the info to quickly spread amongst all nodes that a block was mined.

https://data.bitcoinity.org/bitcoin/block_time/5y?f=m10&t=l