Slavica Jokanovic's Fulham secured the £200m windfall up for grabs in the richest game in world football, as they rocked Villa on to the back foot with a fine first half display and then clung on to secure a famous victory.
There was heartbreak for Ghana's Albert Adomah on Saturday as his Aston Villa side missed out on Premier League promotion following a defeat to Fulham in the Championship playoff final. They have bounced back from that disappointment in style this season.
Fulham has been in the Championship since 2014-15 after being relegated and almost secured an automatic promotion place, only to narrowly miss out to Cardiff City.
Grealish raced to head just over with the goal gaping before Hourihane's cross-shot threatened, but Fulham were looking unsafe on the break and Aleksandar Mitrovic nodded wide.
Cairney said he believed "football" had triumphed at Wembley.
The 18-year-old, who has caught the eye of many Premier League clubs this season, played a superb, inch-perfect pass into Cairney's path and the midfielder tucked the ball away.
"When we didn't get promotion at the end of the season, a lot of people wrote us off and said we had to change the way we play", he added.
The Cottagers were down to 10 men with 20 minutes to go as defender Denis Odoi was sent off after receiving a second yellow card for a late tackle on Grealish.
Villa threw everything forward in the nail-biting closing stages but Fulham held on without too many alarms.
According to the Deloitte Sports Business Group, the playoff winners are guaranteed £160 million, potentially rising to 280 million if they avoid relegation next season.
A place in the Premier League brings potential earnings of £280million if Fulham can stay in the top division, but the London side will earn at least £160million after its success at Wembley.