There's a guy in my town who murdered a teenage girl then cut her up and threw her in a dumpster. He's got less time than these people.

I'm reading sentencing guidelines for material support of terrorism.[0] It looks like they normally max out at 15 years (20 if in support of certain orgs). I saw somewhere that a study of 261 cases found an average sentence of 13 years. So, ceteris peribus, these do seem extremely high.

0. https://www.congress.gov/crs-product/R41333