Why is West Virginia a thing?
Who knows the details of how WV became a state?
Why was West Virginia allowed to become a state?
It was not done quickly./ There were two conventions in Wheeling, in 1861; the first essentially to get counties to send delegates to the second. At the Second Wheeling Convention, the delegates took the powers of the government of Virginia, as freedmenspatrol says, electing a governor , Francis Pierpont and he then convened the legislature of Reorganized Government of Virginia. There was a possibility that, indeed , the government of Virginia was just going to be in Wheeling from then on.... but later in August the Wheeling Convention reconvened and after much debate it issued the "Ordinance to Provide for the Formation of a New State out of a Portion of the Territory of this State”, which required a referendum be put to the voters. That vote was in favor of creating a new state. It should be noted, that the voters wanting to stay with Virginia had Union Army bayonets nearby influencing their votes, and those counties most in sympathy with the Confederacy ( like Berkeley and Jefferson) were only given the option to somehow, under Union occupation, elect delegates to say otherwise if they did NOT want to be in the new state. Once the referendum was completed, the Loyal Government of Virginia agreed to the creation of a new state from Virginia territory. Pierpont then moved his government to Alexandria, Virginia and from there governed all parts of the state under Union occupation, and from there to Richmond after the fall of the Confederacy, where he was governor of Virginia until 1868. That government of Virginia that started in Wheeling, therefore, eventually became the one in Richmond, and simply continued on after the War with elections, etc.
The State of West Virginia therefore had to pass a couple of legal tests: it had to get approval of the US Congress, President Lincoln, and the courts. That took a couple of years - one obstacle was deciding whether WV slaves should immediately be freed, with the Union Republicans saying yes , and WV slaveowners saying no. Fortunately a compromise was reached on that ( eventually superseded by the 13th Amendment) and after more debate WV 's petition to enter as a new state , and their submitted state constitution, were accepted in 1863. So this did not happen overnight: from the Wheeling Conventions to statehood there were three years of debates, conventions of delegates, constitutional conventions, referendums, and finally Federal approval.
Although it sounds fishy, there was an effort to act in accordance with the precedents set by the creation of other states before ( like Tennessee from North Carolina) : they did have to get the permission of the sitting Government of Virginia to split away, and they did have to have a referendum on the question put to the voting population. That the sitting government was not the one in Richmond, or that the voting on the referendum was not done under what we'd call peaceful conditions has to be conceded, but it is hard to imagine any other solution to the problem, and there WAS a problem. The Wheeling Conventions were called not only because some Union loyalists wanted to leave Virginia, but because the Richmond government had effectively lost control and the area was descending into chaos, with northern and southern factions battling in the hills and hollers. Plenty of people who had no strong allegiance to either north or south were willing to vote for any effective government in preference to that.
Rice, Otis K. & Stephen W. Brown. West Virginia: A History. Lexington: University Press of Kentucky, 1993.
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