Hi Amanda,
This does look like a fruiting body from a fungus in the Grifola genus, which does include some rot causing genus. The article below explains the relationship between Grifola fungus and oak death. 
https://ag.umass.edu/landscape/fact-sheets/root-butt-rot-caused-by-grifola-frondosa-hen-of-woods
There is no way to eliminate the fungus. Rather, the best practice is to maintain the health of existing trees by ensuring they are watered and have healthy growing conditions. 
If many trees are dying of various species, it may be wise to contact a certified arborist to take a look to identify underlying causes. Arborists are certified through the International Society of Arboriculture, or ISA. ISA maintains a database search tool that makes it each to find an arborist. 
https://www.treesaregood.org/
Please feel free to reach out if you have any questions. 
Thank you,
-Julie