Former cat 1 cyclist here.
Lots of people here have noted that the transition between running and cycling is not an immediate one, this is absolutely true. Mechanically speaking, cycling is closer to resistance training whereas running is more plyometric/elastic. Sure, both sports are about turnover of the legs but there is a lot more to it. A cat 1 cyclist and professional runner might do strength training at similar intensities and weights, but how the force goes through the ground is drastically different; with the two requiring a vastly different balance of slow/fast twitch capacity.
I saw Joe Klecker and a number of other professional runners doing intervals on the bike, and klecker needed barely 260-280w to hit threshold heart rate numbers. in an out and out sprint, I doubt he'd break 800w, nor does he need to.
I raced competitively as a cat 1 until about two years ago when I decided to take up running as a sophomore in college--I am 21 now. first 8 months it was impossible for me to figure out the forfoot strike, and a year later I'm barely breaking 1:20 in the Half Marathon. My FTP was 5.4wkg; 318w at 58kg and 230w for 5 hours. This still gets you nowhere domestically. Running has since taught me that none of this capacity matters or is applicable to running
I'll still hop on a bike after months hiatus and rip 4.5w/kg like muscle memory, sometimes i wish i could lose this muscle memory and trade it for 4:40/mi threshold pace.
Olympic triathlete Morgan Pearson is the man. Took him some years but i take it he's made his way to 5.5+ w/kg.