I'm both surprised and not really surprised. On one hand, for a while I did believe like many others that Maiden would rather call it quits than start replacing members and that Steve in particular probably wouldn't tolerate a replacement drummer after 42 years.
On the other, Nicko was struggling badly throughout the TFP run and for some songs he never really found any sort of groove that worked for him. So when you have the 50th anniversary tour announced, with RTTH explicitly confirmed by the title of the damn thing, and knowing that's a song he specifically can't really play anymore, it probably should've been obvious.
Kinda crazy how some people called him bowing out in December months ago since it definitely felt like a long shot even after the 2024 leg of TFP got underway. But since it seems like Nicko's own personal decision, I guess all the stubbornness in the world from Steve or Maiden in general couldn't have altered it.
Sad to see him go, but at the same time, his career with Maiden is so legendary and incredible that there aren't really words for it. The best heavy metal drummer, bar none. Whoever's replacing Nicko has some massive boots to fill, that's for sure.