According to https://www.gatesfoundation.org/How-We-Work/General-Information/What-We-Do-Not-Fund https://www.gatesfoundation.org/How-We-Work/General-Informat...

According to https://www.gatesfoundation.org/How-We-Work/General-Information/What-We-Do-Not-Fund https://www.gatesfoundation.org/How-We-Work/General-Informat... they do not fund “Political campaigns and legislative lobbying efforts” As to reasons, why, I am not sure but I imagine there is a pragmatic angle to it in addition to reputation and other considerations. Investing in politics increases the risk that the funds get wasted if the political climate changes.