When you are new, struggling for your first big finish, it could be frustrating to see in tournament after tournament a fish with a big stack making it to the final table when you bite the dust, especially if it's the fish who stacks you.
There's no secret startegy being used here, I won my first ever 50c tournament in 888poker for $75, then I got second place in another tournament for $86, playing Ktrash and Qtrash
hands all the way to the final tables. I was merely a fish on a heater.
The other day I saw this guy calling every hand, building a 500bb stack, crushing QQ+ pairs multiple times, completing all his draws, hitting two pair when dominated, it was sooo disgusting ... and funny. At some point he got wise, tightened up, got a little more luck here and there, made it to the final table. He punted away his stack for 9th place. I was having a laugh the whole time watching him get there with worse at every moment.
Learn to appreciate the fish, remember that you want them to play like that, don't feel discouraged. Understand that you probably still have a lot to learn, that it takes time to see the results, and that a fish can get lucky one day, but consistently doing well is only possible for those that put the effort.