Case and Left Join Problem

I am attempting to find the cost per lead, however they are on different tables. I am using the Case and Left Join Functions to do so.

The following Queries are working correctly. These are below:

SELECT

"Campaign",

COUNT("Id") AS 'total_leads'

FROM "Deals"

GROUP BY"Campaign"

	Campaign	total_leads
1		885
2	Attention Small Business	69

SELECT

"Campaign Name",

SUM("Amount Spent") AS 'total_spent'

FROM "Campaign Insights (Facebook Ads)"

GROUP BY"Campaign Name"

	Campaign Name	total_spent
1	Cold... 3/13/24	5467.8
2	Cold... 5/8/24	2672.97
3	In Need?	39.04
4	Attention Small Business	299.73

However, when I combine these using the Case and Join Function, the "Attention Small Business" Campaign is giving different values. I am unsure of the reasoning behind this. Any help is useful. Query and OutPut below.

SELECT

"Campaign Name",

SUM("Amount Spent") AS 'total_spent',

COUNT("Id") AS 'total_leads',

CASE

WHEN COUNT("Id") > 0 THEN SUM("Amount Spent") / COUNT("Id")

ELSE 0

END AS cost_per_lead

FROM "Campaign Insights (Facebook Ads)"

LEFT JOIN "Deals" ON "Campaign Name" = "Campaign"

GROUP BY "Campaign Name"

	Campaign Name	total_spent	total_leads	cost_per_lead
1	Attention Small Business	20681.37	276	74.93
2	In Need?	39.04	0	0
3	Cold...3/13/24	5467.79	0	0
4	Cold...5/8/24	2672.96	0	0