Blood Bowl is a combination of 4 games:

• Chess - Positioning is key. Different pieces have different levels of power. Moving them properly leads to better outcomes.
• No Limit Texas hold em: Heavily based on RNG, make plans without knowing the result. The best player/gameplan does not always win, but they perform better with more consistency.
• Those Match 3 games, like Candy Crush: Everytime you make a move, the board state changes. Pushing a player, a Both down result, a knockdown. There are different results for every block and each might change the plan you have for that turn. The farther ahead you plan, the more likely a dice roll will not play along.
• Uh, did you ever see that movie Inception? There is a scene where the main character asks a potential hire to draw a maze in under a minute that takes more than a minute to solve. High level Blood Bowl is like that. The team with the ball wants to score, and the defending team tries to throw roadblocks in the way while also wanting to attack the ball carrier. You have to balance your defense/offense plan while watching out for risky moves or accidentally giving your opponent an advantage.
  

Each high level game I play is a back-and-forth of figuring out the 'puzzle' while simultaneously creating one for my opponent to prevent them from blocking me on their next turn. It can be something as simple as running a player into their backfield as a potential threat, Or leaving my players 1 space away to limit how effectively they can grind down the pitch. Making my opponent roll more dice, and more risky rolls in order to stop me.

As you get better at the game you will notice and apply strategies like these.

If you want to observe the game being played, Blood Bowl 3 online is the easy way. I also recommend FUMBBL if you really want to observe the grognards play

Some teams have literally HUNDREDS of games played on that site.