One Massive Campaign:
A massive campaign likely has repetitive ad groups as well as ad groups that would do better under different targeting and budget conditions. Consider the focus of the campaign, and whether it should be oriented around a location, a service offering, or products with different margins. A typical setup that many advertisers should consider is arranging your campaigns similar to your website menu structure. This works very well for ecommerce advertisers that have unique product sets and it can also be very effective for lead generation organizations that are providing more than one specific service or offering. Separating into multiple campaigns also gives you more control over your budget, since your budget is set at the campaign level. You can allocate more or less budget to different campaigns based on seasonality, profit margins, and overall search performance.
(Some of the settings determined at the campaign level.)
Campaigns with too many ad groups:
Since ad groups all share the budget in a campaign, there’s an inherent limit to how many ad groups a campaign can support. While consolidation is still a meaningful approach, consider whether certain ad groups could be their own campaigns.