'Bachelorette' host Chris Harrison explains how the casting process changed for Rachel Lindsay

— -- Rachel Lindsay was the first Bachelorette to be revealed while she was still a contestant on "The Bachelor," and according to host Chris Harrison, the casting process was unorthodox too.

Harrison told ABC News that because Lindsay, 32, is slightly older than previous Bachelorettes, producers wanted to cast men who were around her age and professional level.

As a result, he said, most of the contestants this season are "a little bit older, a little bit more accomplished" than in the past.

"You couldn't have a 21-, 22-year-old frat guy coming in, looking for love. That's not who Rachel's going to end up with," Harrison said. "If you look at the bios, and I know some of them are funny, but even the tickle monster, Jonathan, is actually a doctor. We have a lot of doctors ... We have our personal trainers and our male models as well [there is one of each], but that's important. You really want to have that wide spectrum because she doesn't necessarily want a lawyer. She might, but that might not be what she's looking for."

Diversity is a factor this season too. Lindsay is the first African-American person to star on "The Bachelor" or "the Bachelorette," and the group of 31 men pursuing her is the franchise's most diverse yet. Harrison said that was a move the producers took very seriously.

"If you don't see yourself represented, no matter where it is, why would you go? Why are you going to put yourself out there and try and be on this show that you know you can't be on or you're not welcomed at or you feel like you're not?" he said of potential suitors. "We've been working on this for a while. Now you're seeing the fruits of that labor. Rachel is our Bachelorette, and we have the most diverse cast ever. It's not a theme. It's just something you will see throughout."

And though this season may be new in some ways, Harrison told ABC News that drama will remain an important element of the show. Though he gushed that Lindsay is "an awesome woman," he added that "she has some little idiosyncrasies that were a challenge for us."

"She likes to hold on too tight sometimes, and you really have to try and get this lawyer who controls her life to let go, and that's not an easy thing. There's some bumps and bruises along the way," he said. "But it's a phenomenal ride. We have amazing celebrities. We have great dates. We have drama. It's this great love story that will hopefully have a happy ending."

The new season of "The Bachelorette" premieres on Monday at 9 p.m. ET on ABC.