Rick Wakeman did perform at a sanctuary in Vietnam in 2015 for Animals Asia, and the concert was genuinely for rescued moon bears - not some made-up stunt. The whole thing happened because Animals Asia reached out to him about their rescue work, and he was willing to show up and play. It's weird on the surface, but when you think about how these charities work, getting a big name to perform at a sanctuary is a solid fundraising move.
What makes it less random than it sounds is that Wakeman had already been involved with animal welfare causes before this. He's not the type to just do anything for a paycheck - he actually cares about the work. Moon bears get their name from the distinctive white or cream-colored marking on their chests, and they were being rescued from illegal bear bile farming operations in Vietnam, which is genuinely brutal stuff. So it wasn't like he showed up to play for some novelty photo op.
The real story is that benefit concerts at sanctuaries are becoming more common, even if most of them don't make international news. The oddness factor here is just that Rick Wakeman is such a recognizable name in progressive rock, so when his name shows up attached to "concert for moon bears," people's brains short-circuit a little. But it actually makes sense from a charity standpoint - you get media attention, funds for the rescue work, and animals get some good attention directed at their plight.