Playing this in the background and Skin just said be believes Nico looked at the Thunder and Spurs and concluded the Mavs won't be able to build a better team than them over the next ~10 years, so once Kyrie and Klay and those guys are done, their window is shut. So, he's basically going all-in to win in the next 3 years because if they don't now, they won't win a title again for a long time.
I think a lot of us would argue that as long as you have Luka, you have a chance to compete for the next decade, but I'm guessing Nico is also aware that the Mavs don't have the future assets to keep building around him once this current supporting cast is gone. Not sure I agree, but just reporting what he's saying.