Is TOR critical to Bitcoin and Lightning?

I was reading the other day that one key difference between the TOR and Bitcoin/Lightning networks, when it comes to network growth (in terms of number of individual nodes supporting it) is the alignment of incentives, that makes that people can even profit from running their own nodes (especially in Lightning), whereas that's not the case for TOR, which apparently has made the project stagnate in terms of growth.

What happens if X years down the road the number of individual nodes of the TOR network reduces drastically (due to people losing interest, simply dying or whatever), to the point of even compromising the whole network?

What effect would that have on all the Bitcoin and Lightning nodes that run through TOR (which apparently are the overwhelming majority)?

Would that make that particular nodes disconnected from the network, hence increasing the possibilities of a 51% attack, if the remaining (a minority) where to collude?

I hope this is not a risk to Bitcoin nor to Lightning or a solution already exists. Thank you!