Civil War was a crossover book that touched damn near every Marvel title out there (But don't you just love how Daredevil stays above all the bullshit and does his own thing?)

The core Civil War miniseries was only 7 issues.

52 is completely self contained, and because there's 52 of them it can tell a lot more story. If this were a monthly book it would take nearly 4.5 years to complete. There's nothing "mini" about it.