Why varun gandhi joined bjp?

It's fairly straightforward. He joined in 2004 along with his mother, Maneka. She had already broken from the main Gandhi family and the Congress party years earlier. I reckon his own nationalist views were a much better fit for the BJP's platform, anyway. Politically, it was a smart move. His path in Congress was always going to be blocked by his cousins. He simply needed his own turf to build a political career.