Putting the FTC to one side, it seems beyond comprehension that any company; particularly Microsoft, would be stupid enough to try and ignore the immense power of the CMA/CAT to try and close this deal, which has got me thinking.
Take a worst civil case scenario of them closing without consent from the CMA. They get fined an extra $17b for year one, and maybe another $20b in year two before the issue resolves itself. But in return they've mortally wounded the consumers choice of high end AAA gaming platform to the tune of around $2b per year for those two years and completely dominated mindshare.
Even if they were then forced to sell off ATVI at a massive loss ($30b) the damage to PlayStation would be permanent relative to where XGS would be positioned financially and the whole thing would still only have cost them the same depreciating $70-80b and made it look like the CMA lost, given them time to lobby in the UK to hinder the CMA being powerful enough to block all their future acquisitions.
At the moment, if the CMA blocks this deal, Microsoft's +30year MO is done. They have seen their share price multiply every decade since the start, and that came initially from product success and foreclosing rivals in their primary markets(OS/Productivity software) to dominate - rather than compete, giving them financial success and plenty of cash to reward shareholders and launch products in new markets, until they became so big that to avoid giving shareholders too much dividend - which they would then spend on competing shares like Google, Amazon, Meta, Apple, etc, today - they needed to spend all that extra money on acquisitions to keep the share price growing to keep the shareholders - and new investors - invested long term.
In short(IMHO), Microsoft have outlived their usefulness as a company to create or innovate, or do anything but consume others, and distribute spoils to shareholders, rinse and repeat.
Without the ability to consume at ATVI value level - because the CMA might block all those deals - Microsoft has no way to use their money to quickly keep their share price growing, and would either have to use it for large buybacks as a one off, or raise the return via dividends (IMO) which will get spent elsewhere, or leave it in the business, where it is at risk of depreciating or being eyeballed by shareholders to push for a higher dividend.
/edit
So my point being, these actions are possibly because this deal is the tip of the spear, and it failing means their demise. So it is the actions of them being in a corner with no better option.