There is no way to know why the size limit was reduced from 32 MB to 1MB. There was only a commit but not an explanation. Over the years people have come up with different theories including the one that says it was to stop attacks against the network - many of the early blocks are empty and given blockchain is essentially an empty book, people could fill it with garbage data and bloat the size of blocks to size limit of 32 MB.
I thought this part in the cancellation notice somehow pointed to this result -
"As fees rise on the blockchain, we believe it will eventually become
obvious that on-chain capacity increases are necessary. When that happens,
we hope the community will come together and find a solution, possibly with
a blocksize increase. Until then, we are suspending our plans for the
upcoming 2MB upgrade."
Most profitability calculators only take the price/difficulty into consideration, but Fork also includes the fees. Fees being high now gives an edge to mining BTC over BCH.
Also note the BCH just yesterday moved from the BTC difficulty scheme of changing difficulty every 2016 blocks to one where each block gets a difficulty based on a 144 block rolling average. This will presumably dampen the difficulty oscillations somewhat.