Losing filter context via group by/summarize

I work with different data than sales data, but for everyone to be able to understand I used a contoso data set for it.

What I would like to achieve is to count the number of unique customers that bought more than one product.

CustomersMoreProducts =

VAR MaxDate = MAX('Date'[Date])
VAR CustomersMoreProducts =
--Unique customers with more than one product in period.
CALCULATETABLE(
FILTER(SUMMARIZE(Sales,
Customer[CustomerKey],
"#Products", DISTINCTCOUNT(Sales[ProductKey])
),
[#Products] > 1),
DATESBETWEEN ( 'Date'[Date], DATE(2008,1,1), MaxDate )
)

RETURN
COUNTROWS(CustomersMoreProducts)

However, I would like to analyse it by last product.
So imagine a table visual with productname (=last product) and the measures(=customers who bought more than one product). 

I know that in the filter context there is only one (counted) product so therefore the measure is returning BLANK.

Could someone point me in the right direction.

I also have another code sample in which I first calculate a table variable with the following output:

CustomerKey, LastBoughtProduct, LastBoughtDate.
Then I tried to use TREAT AS to assign field LastBoughtProduct to Product[ProductKey], however not the result I expected.