Could my iPad be compromisted by Pegasus spyware?

You must be an extremely important person if you were attacked by Pegasus? Since you likely aren't important enough on the world stage, you most assuredly have NOT been attacked by Pegasus and any such claims are false. Whoever sent the message is scum and is only trying to scare you into complying with them. Ignore them. They haven't infected your phone and they can't do what they threaten to do.

Read this --> Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

No, you have not been hacked. It's just the latest version of a scam that's been going around for years.

First it was the FBI or CIA that had some sort of criminal activity on you. But golly!, you could make the charges go away if you sent a bunch of money to a random Bitcoin account. Then it changed to saying they had videos of you doing naughty things and once again, pay a Bitcoin account to stop them from making videos public. Now there's this one. I got one a few days ago.

The basic text of the email never changes. Like, "You don't know me, but I'm sorry to say you've been hacked. I put a trojan virus [my injection here - there's no such thing as a trojan virus] on your computer. You won't be able to find our remove it…" And the nonsense continues on.

In short, ignore and delete. Expect to get multiples of these. Sometimes a dozen per day of the same thing.

No. You were not ‘hacked’. The email you got was a scam.