That may be a part of it, but it's mostly due to homeownership. Germany is a super risk-averse country, thus few people invest their money. Most people hold everything in cash, thus they get very low returns. It's also the reason why they are hit so hard in a low-interest environment.
"When dividing the Eurozone into a group of countries often labeled as ‘core’11and a group of Southern-European12countries, it turns out that Southern-European households are more capable of keeping up their standard of living compared with those living in the core countries (see figure 18)"
"It is striking that German households have fewer assets than Eurozone households have on average. They not only own relatively little real estate(see figure 20)but also hold less financial assets than is common in the Eurozone(see figure 21)."
https://jakubmarian.com/wealth-per-capita-by-country-in-euro...
It's describing the median wealth based on a Credit Suisse Wealth Report
You can also find these results in the ING research ("Surprising differences between countries", page 14ff): https://www.ezonomics.com/pdf/Household-wealth-in-Europe.pdf
"When dividing the Eurozone into a group of countries often labeled as ‘core’11and a group of Southern-European12countries, it turns out that Southern-European households are more capable of keeping up their standard of living compared with those living in the core countries (see figure 18)"
"It is striking that German households have fewer assets than Eurozone households have on average. They not only own relatively little real estate(see figure 20)but also hold less financial assets than is common in the Eurozone(see figure 21)."