It is. Up and until the early 2000's West Virginia was one of the most democratic states in the nation. Manchin was a very popular governor from 2005-10. That carried over to his run for the senate. West Virginia had a very long history as reliable democratic until recently. Presidential wise, West Virginia has gone Republican six straight times. Trump won WV 68.6% to 29.7% for Biden, in 2016 WV went to Trump 68.5% to 28.4% over Clinton.
Kind of like Georgia until 2002, WV continued to elect very conservative Democrats to statewide and local offices. Georgia elected its first ever Republican Governor in 2002 along with its first ever Republican state legislature. WV was the same. We sent Democrats Richard Russell, Sam Nunn, Zell Miller, Max Cleland as senators to Washington while WV was sending Manchin, Rockefeller, Goodwin and Byrd. What they all had in common was they were conservative democrats, a dead bird democratic party wise these days except Manchin.
According to PVI, West Virginia is plus 35.5 Republican over the national average. Okay, maybe not the reddest state, but close.https://fivethirtyeight.com/features/how-red-or-blue-is-your-state-your-congressional-district/
Once Manchin is gone, you can bet a Republican will replace him. He barely won his last election 49-46. All three of WV congressmen are Republicans who swamp their Democratic opponents, 69-31, 63-36 and 71-29 in 2020. You have the last two presidential election results. In 2020 Republican senate candidate Capito defeated her democratic opponent 70-27.
I'd say it safe to say that Manchin will be the last Democrat to come out of West Virginia for a long time to come. You're talking about a state that elects Republicans these days by an average of around 70-30.