Trezor claims that no one was affected but approximately 66000 users' email and nicknames were leaked. This means the hacker has a list of 66000 Trezor users and he will surely try to use those emails to do something.
The hacker doesn't necessarily have the information of 66,000 Trezor users. They have information on (according to reports) a maximum of 66.000 users that contacted Trezor support from December 2021. Many of them are surely owners of their hardware wallets, other's could be interested parties, like you and me, who sent an email and asked for information or clarification on some points.
Trezor stated that they still don't have information if there were any victims, but they know of 41 phishing emails that were sent out. That was the information that was available when I created this thread.
hacker was able to develop a fake Trezor Suite App and ask users to download it, connect their wallets, and then steal it easily.
They didn't develop a fake app. This is a phishing scheme. A social engineering attempt to get you to email them the seed.
Why does Trezor retain customer data from December 2021, and what is their need for this data, since the user does not interact with the company directly after purchasing the devices?
It's not Trezor's data. It belongs to the 3rd-party service they use for the customer support portal. Their TOS and Privacy Policy will shed more light on how long they retain customer information.