WWE brought in Rob Van Dam during the invasion time period and he was the only ECW star whom the promotion wanted to push as a top star. He received a very strong mid card booking upon joining WWE and he won both of the mid card titles of WWE soon after joining the promotion which are WWE Intercontinental title and the WWE European title.
Van Dam was also the first wrestler who challenged Triple H after he was awarded the newly introduced World Heavyweight Championship in 2002. He was also a part of the first ever Elimination Chamber match. But his main event push slowly declined as he mostly focused on the Tag Team titles and the mid card titles.

Revealed: Why Rob Van Dam Left WWE Back in 2007
In 2006, WWE finally decided to award him with a proper main event as he won the Money in the Bank Ladder match and later he cashed it in on John Cena to win the WWE Championship. Surprisingly, Van Dam decided to leave WWE in 2007 even after having such a strong main event run. The 54 year old finally revealed why he left WWE in 2007 while speaking on his 1 Of A Kind With RVD podcast,
Rob Van Dam won the WWE Championship in 2006
“I got suspended for 30 days, and then both championship belts were forfeited. Then I felt like ECW was in the toilet, swirling down the drain, and they wanted to flush it, so my passion was gone.”
“I said, ‘I’m finishing my contract, and then I need a break, I’m not going to re-sign.’ We talked many times about what it would take for me to re-sign, and I chose spirit first. They offered, ‘How about you sign for six months, or a year, and then come back?’ And I was like, ‘I can’t do it, I need to know what it felt like to be free in order to grow.’”

Rob Van Dam was inducted into the WWE Hall of Fame in 2021
Rob Van Dam returned to WWE in 2013 after six long years and spent only a year in the promotion. From 2019 to 2024, the former WWE World Champion appeared a number of times in WWE and he was also inducted into the WWE Hall of Fame in 2021. Van Dam will always be remembered as one of the biggest legends of professional wrestling.
H/T to TJRWrestling.net