Why is this the case? It seems like if Texas was connected they'd be able to pull some of that missing 45GW power which might be enough for an hour of electricity every 8 hours which would be a total game changer for a lot of homes.
Yes. At the peak, Texas wholesale electricity spot-prices went up by 10,000% - 10x is child's play. What would have happened was non-essential use in California would have been priced out by desperate Texan households who'd pay almost anything to keep residences heated.
Energy companies absorb the fluctuations, except for that one company that thought it was a great idea to pass-though prices to the customers. It was a great idea when the prices were low, but many of their customers will likely experience sticker shock on their next bill.