Perhaps the CAA is a bit too quick to prevent UK airlines that have gone into administration from somehow reviving themselves. That said, it had been clear from at least spring 2019 that Flybe was in deep trouble. Once Covid turned up, Flybe didn't stand a chance.
The time for reviving an airline is in the first few weeks after flying is suspended when the brand could maybe come back to life and the routes with most potential had not been claimed by other airlines. Even if Cyrus were ready to go tomorrow with Flybe v2, a delay of 3 months combined with a significant fall in air travel demand means the window of opportunity has almost certainly closed