I am wondering why did HFPA put The Martian under comedy? Is it because they wanted to give it an award? Has something similar happened before?
The Martian was classified as a Comedy by HFPA because the Hollywood Foreign Press Association’s eligibility committee voted to make it so. According to the LA Times the HFPA vote was very close as The Martian ended up classified as a comedy by just one vote.
Without specific comments from those who voted it would be nothing more than speculation to discuss the "why" however it's worth noting that the Golden Globes comedy category is the weaker of the two categories it awards and this isn't the first time a movie has been classified as a comedy at the Golden Globes.