I think it's great for a ground-floor investment in a YouTube competitor. It draws more people to the platform, gets a chunk of money flowing up front to help boost the service, and they can always sunset the lifetime option if the site gets popular and revenue starts to get tight. As long as they continue to honor it for everyone who paid initially.
Like I said in my original comment, a Nebula subscription is only $6/mo. A lifetime access payment is over 4 years of subscriptions up front. That's a nice chunk of change to help get them established.
I saw someone's video about how Nebula works (I think Legal Eagle? He was advertising it hardcore on YouTube for a while) and the subscription service is how they pay content creators. He said it's a more stable income than YouTube, where your videos earn advertising money based on trends and visibility. If you're not YouTube famous (and the algorithm doesn't make you visible), you're not going to make any money on the platform. But Nebula gives you a more solid income, plus the freedom to make the content you want. No AI moderators flagging videos because it thought it detected the word "suicide" or something. No forcing you to include key words or pushing regular videos on a tight schedule to ensure the algorithm keeps recommending your channel.
When I lived in Germany for a couple years, I was surprised to learn that the large church in the center on my village was about 1,000 years old. This one building has been standing longer than America has been a country. Over 4x as long, too! European culture amazes me because there's such a lengthy history, and so many things are much older than I'd imagine. American history is so short in comparison, and we're more likely to tear down and build new and cheap than create a solid structure that will last for hundreds of years.