Frankly, I never thought DC TV shows were capable of creating such a big universe, but then one day I watched a episode of Arrow on netflix and after that I bing watched all seasons (5th season was running at that time), and when Invasion was announced as crossover I watched other shows too (flash mainly). Amazing thing how it paved the way for the Arrow-Verse (always gonna call it this only) shows and then Crisis on Infinite earth was just the thing required to solidify the universe. Arrow being the one to reboot and then a lot of cameos, even DCEU cameos, I mean it's something they achieved at just a TV level budget. I am never gonna forget the impact that it put on me and for the Crisis on infinite earths I watched all tv shows in the verse (all cameos shows). In my opinion they compete head to head with the Avengers - Endgame just on TV and created the Justice League way better than DCEU movies.
Always gonna love this show ☺☺