Yamato didn't lose to Kaido, Loki lost to Imu, multiple times technically. There are differences, obviously. But Loki fills the Yamato role for Elbaf, he is Yamato 2.0.
Oda didn't protect anything, Hybrid Loki is just not strong enough to beat Imu like you claimed, in fact he's not even strong enough to last more than a few pages, and he apparently gets one shotted according to leaks. This is Oda feeding Loki's Hybrid to Imu immediately before Luffy faces Imu for real, aka, hypetooled.