"caught me off guard"

"This is nothing new, nothing I hadn't heard before, but what really caught me off guard was that there are still hightly educated people in posistions who..."
to catch off guard someone ~ to surprise them?

Not "to catch off guard someone", but "to catch someone off guard".

Yes, it means to surprise.

thnx ved, but I don't see how they're related

in a fight, you expect to be attacked so you 'have your guard up', which means you hold your hands in front of your body or face to shield you from attack.
'being on your guard' is the same as 'having your guard up' and is used figuratively to mean being alert and ready for something, because you are expecting it.

so being 'off your guard' or simply 'off guard' means not being alert to something, because you are not expecting it.
so something that catches you in this state is something you are not expecting =>

something that catches you off guard = something that surprises you

There is also the term "on guard," which means to have the duty of watching over something to protect it. "Who's on guard tonight?" In this situation, being "off guard" means being not watchful, hence not alert and unprepared.

thnx a lot guys