A crawler reaches a page in one of three ways: a link from a page it already knows, an entry in a sitemap, or a URL submitted directly. Everything else is invisible. That is why an orphan page — one no internal link points to — can exist for years without being indexed, and why a crawlable navigation matters more than a beautiful one.
Crawling is not indexing. A page can be crawled and then discarded because it duplicates another, because it carries a noindex directive, or because the engine judged it not worth storing. Search Console's index report distinguishes the two, and reading it correctly is the difference between fixing a real problem and rewriting content that was never the issue.