“I started using it, doing some research, I noticed that the workouts were weird and even a bit dangerous sometimes… Okay, this is it: we need to build [the incumbent's] UI/UX with an actual proper workout engine.”

Clone the category leader's UX — then fix the broken core nobody else noticed

Pure copycat builds add no value, but cloning a beloved interface while fixing what's actually broken underneath is a viable wedge. The trigger to go all-in came from realizing the incumbent's core logic was bad — not its design. Familiar UX plus a genuinely better engine is enough to displace.