From my perspective at least, this is not a bet, it's a business transaction. My motivations are 90% profit and 10% because I do not foresee BU as it exists today succeeding with the lack of code review and still unsolved EC divergence. Nothing prevents a miner from switching to the Core chain and orphaning the entire BU chain if it becomes profitable to do so.

As for big vs small, I supported 2MB last year when there was no working implementation of LN. Today SegWit + LN appears to be ready to go. I believe that the BU miners are not looking at the bigger picture. On chain fees can continue to rise even while a large number of transactions move to LN. There is no issue paying a $10 fee to open a reusable channel, while the same fee for a single transaction is extreme. SW already offers 2MB, the only difference seems to be where the signatures are stored.