What, did Briedis suddenly lose all his power? He literally snapped Opetaia’s jaw early in the first fight. Opetaia didn’t go down and didn’t even look like going down. He has a granite chin.
I wouldn't put too much stock in those measurements, a heavyweight could change 10lbs within a day without doing anything too drastic. And height is nearly always exaggerated, Itauma doesn't look that tall compared to other fighters. Reach is sometimes just a complete guess, there are fighters who have reach measurements listed who claim to have never had it measured before. I think what happens a lot with height or reach measurement, is someone takes a measurement in random circumstances, could include shoes etc or just makes one up and it ends up getting picked up by every pundit, org, record keeping system and repeated ad nauseum without any verification. Itauma used to be listed as 6'6 everywhere for example.