Let me explain how Alabama primaries work. Only a few people actually go vote in a primary based in Alabama based on what party they truly believe in for statewide races.
The overwhelming majority of counties in Alabama are under one party control where either the Republican or Democratic primary determines who will control the county offices. Almost all of Alabama’s high population majority white urban counties are counties where local races are decided in the Republican Primary. Roy Moore is unpopular in metro areas. That’s why he’s losing.
Roy Moore’s base of rural supporters, they may be Republicans but most vote in the Democratic primary because if they don’t they lose their effective vote for county sheriff, county clerk, state legislature, etc.
This means that the Republican primary electorate in Alabama is more moderate than the general election Republican electorate and the Democratic primary electorate is far more conservative than the Dem general election electorate.
Roy Moore lost because all his voters were voting for Ron Sparks against Artur Davis while they were voting for sheriff.
Good inside baseball to know.