The Tractatus builds up from a very simple scientific grid to prove that propositions are laid upon whatever is out there. And the sum total of what we can know by our logic is limited by the number of possible true and false propositions in the model we are using. When you complicate a single dimension scientific grid by including another dimension you have a simple flat earth geometry. Then if you add a dimension for time you now have a huge number of possible true and false propositions but the total number of facts is still limited by your system.
The Tractatus ends by showing that the discussion of moral and theological propositions is by definition and logically excluded from even the most complicated scientific grid.
What happens in the Investigations is that Wittgenstein had come to see that language (growing like a city) includes all sorts of other kinds of proposition, which can be equally true or false. Which for me restored the certainty that moral and theological propositions and discussions are on a level playing field with all others.
This should have ended the possibility of foundationalism for ever. The only foundation is that humans use language in millions of different ways to express their observations, preferences, faith, and moral values. Wittgenstein replaced Descartes' famous statement "I think, therefore, I am" with "There is human language, therefore we are." The Investigations also exposes the error of the extreme reductionists. When humans talk and listen to each other they are able to evaluate most kinds of hypocrisy and self-interest. We are all hypocrites and self-interested, including the reductionists, but we can still discuss and live by moral values. And that is true both in face to face oral discourse, and in evaluating the Gospels.