people aren't wrong about the drivers, but the "thinkpad+linux" subculture comes from back in the day when IBM used to make them, and the early Lenovo years. They were well-built, very robust laptops. They used to have features like liquid drainage channels (so if you spilled drinks on the keyboard it would drain out the bottom of the laptop, limiting the damage), and Lenovo used to publish detailed manuals explaining exactly how to do your own maintenance and repairs on the laptops, with the part numbers that you needed for replacements, even down to the spec torque settings for individual screws (which is a hilarious level of detail for a laptop, as opposed to something like a car or bike).

Here for example is the is service manual for the X220, which is still available on Lenovo's website: https://download.lenovo.com/pccbbs/mobiles_pdf/0a60739_01.pdf

Just go look at the table of contents, they walk you through things like how you can replace the keyboard (people used to do this to change the keyboard to different languages) or how you can replace the front bezel with the fingerprint reader version, or how you can install a WWAN card (this was a network card that let you connect the laptop to the cellular network).

And because thinkpads were such a popular corporate laptop, there were always plenty of them on eBay being sold off when companies got new laptop fleets, that were usually only 3-4 years old and still had plenty of life left. That meant you could get good deals on really decent laptops, in good condition, and there was plenty of market also for spare parts for them.

Today, that kind of repairability and parts market is a boutique feature (ex. the framework), but I think it's pretty self-explanatory why the repairability and robustness of the laptops made it popular in FOSS circles. It's really a shame, I would probably still be using my X220 today if I hadn't broken it back in 2019. IMO it's still the best laptop ever made.