Earlier quoted context omitted.
There's strategy, and in a broadcast (as opposed to attending a live event), there are commentators to explain it to the average viewer. There are also amazingly spectacular plays, which you can appreciate whether or not you understand the strategy. That doesn't explain why it's more popular than, say, basketball, though...
The problem with basketball as a spectator sport is that the marginal importance of any particular small piece of the game is small, and predictable. There may be awesome feats of athleticism and skill, but they really don't count for a lot, and by the end of the game, you could remove any one (or more) of them and the result of the game would have been the same. When you think about what makes, say, movies exciting,…
Football and baseball are more punctuated, stop-start action.