Maybe this is a hot take. However, a lot of the Chromebooks that were deployed by schools during covid are build like tanks while being super lightweight and having great battery life. Meanwhile the old thinkpads are 10 years old and are probably starting to wear down. Many Chromebooks support coreboot these days so theoretically they have the potential to be more private and secure. Some of them are also arm which means that they are more efficient from an architecture perspective.
Edit:
I like how incredibly controversial this is. I have successfully split the votes
The ones from schools are very tuff. I wouldn’t call a 10-15 year old thinkpad powerful
No way. My T420 with a 3.4ghz 4c8t i7 absolutely outpaces any celeron POS Chromebook. Either you don’t have much experience with good (T-series) Thinkpads or you don’t have much experience with Chromebooks.