It took me a few times to understand their sentence correctly.

What I think OP meant to say:

All pupils found success. My success could be explained by being primed for success with 18 months of duolingo, but all pupils had similar success.

As written, it reads like "all pupils [...] primed for success by duolingo" which is perhaps why you tried to look for irony to match it with their conclusion.

Hah ok. I’m amused.

If they were actually primed for success then 18 months of Duolingo should've given them a significant head start on the other students.

Judging by the tone, I'm assuming that didn't actually occur.

Studying Duolingo for 18 months should have primed them for success, but after just three weeks of an in-person class, it was evident that it had not. It's implied (or assumed) that the class was for 2nd year students or less, so Duolingo must be less effective than traditional instruction.

Class is ongoing and it's for complete and utter beginners, I'm in week 5 right now. Gave up on Duolingo maybe 18 months ago or more.

Duolingo saving a year of in-person classes sounds like a success to me.

It took much longer and did not work, and that's a success in your opinion?