Virginia still has a plethora of very important logistical and military sites. Just in Southern Virginia you'll find the largest naval base in the world at Norfolk (which has its own interstate highway- I-564, because of how large it is), the Yorktown Naval Weapons Yard, Langley Air Force Base, and the Yorktown Coast Guard training center, among others.

Many members of Congress also live in Northern Virginia, and the Pentagon is located in Virginia, so it is an important state for the US politically and from a military perspective.

However, the population of Virginia is only roughly 8.4 million, less than New York City (which has 8.5 million people). So Virginia has fewer representatives in Congress than the states you mentioned.

After the Civil War specifically, though, Virginia was saddled with a large amount of debt from the war, which divided the Republicans who were in power at the time. The Democrats then used a platform of ending Reconstruction policies and disenfranchising blacks from politics in general to win control of the state for a long time. From 1881 to 1969, no Republican won a statewide office.

In 1902, Virginia's dominant conservative Democrats promulgated a new state constitution that equipped local election officials with devices for disenfranchising political opponents, including most African Americans and many Republicans. Voting participation in Virginia plummeted.

Although the debt had been refinanced in the early 1880s, it took Virginia a while to get back on its feet. Coupled with the near total removal of blacks and liberal Republicans from political power, Virginia's influence in national politics declined due to their internal struggles after the war.

This was a very brief overview that I hope answered your question a little bit. For more information, I'd recommend Brent Tarter's A Saga of the New South: Race, Law, and Public Debt in Virginia.

To answer your question, a clarification needs to be made.

As much as Virginia was an economic powerhouse during the Revolutionary War, most of it was defined by it's agricultural status. As the industrial revolution came to North America, Virginia's importance, while still large, began to wane on the national stage.

Areas such as New York and Boston began to rapidly outpace cities like Richmond. Manufacturing and immigration explosions in the North coincided with a an evolving resistance toward the growth of slave based market systems both domestically and abroad.

This is all not to say that Virginia was not an economic and political powerhouse by the dawn of the Civil War. But it does help set the stage. Virginia, with its agricultural and slave based economy had, by 1860, lagged far behind the North in economic development for decades.

Virginia, along with the rest of the South saw rightly how much their influence on the national stage had begun to wane with the election of President Lincoln; a Republican and outspoken abolitionist, where he had failed to win a single southern state, yet still won the Presidency.

The War itself ravaged the Southern economy. Vast swaths of farmlands were sullied. What rail lines that had been established were destroyed. Virginia and North Carolina lost more men as a percentage of their populations and saw more of the fighting than any other state. Richmond itself burned to the ground.

Comparatively, Northern states and cities saw almost none of this destruction. By the end of the war, Virginia had seen its land holding decreased dramatically with the secession and creation of West Virginia, and was left in relative economic ruin as it sought to rebuild an economy that was no longer able to rely on slave labor. By the end of Reconstruction and the dawn of the 20th century, Virginia's importance had slipped even further behind.

The gold rush had brought tremendous growth to regions like California and Colorado. The securing and settling of midwestern lands, with their fertile prairies allowed their farmlands to surpass Virginia's in economic importance. And the Northern industrial cities had only continued in their exponential economic and population growths. Simply put, Virginia got left behind.

That is not to say that Virginia is not a critical state today though. Her economic and political importance remains high. Northern Virginia's vast wealth has grown in accordance with the growth and importance of Washington DC which are now inexorably linked. The ports and US military presence on its coast are of primary National importance. The US Atlantic fleet is based out of Norfolk and one of its primary ship building yards is located nearby.

Politically, Virginia is used as a bellwether for national elections. And it's 13 electoral college points remain highly sought after during Presidential elections.

Virginia has indeed been eclipsed these days in both economic and political influence, but it most certainly remains highly important on the national stage.

One thing to bear in mind is how much 'wealth' that was concentrated in powerhouse Virginia was held in the slave breeding trade.

In 1860, some $4 billion dollars of the US' wealth was slave stock, compared with some $500 million in currency.

After the 1808 ban on the US' participation in the Atlantic slave trade, South Carolina's wealth as a slave importer rapidly gave way to Virginia's prominence as slave breeders. This sort of 'wealth' was also securitized through bonds issued by banks, which held mortgages to southerners, that were collateralized through slaves.

The American Slave Coast: A History of the Slave-Breeding Industry Ned and Constance Sublette