Variance cannot be beat. It can only be outlasted with a proper bankroll.
Fortunately your bankroll for freerolls is unlimited.
Look... if you can get all-in with Ac\Ks vs 7h\2h pre-flop you're 63% to win, which is great. But lets say a freeroll has 500 players and 50 get paid. To make the money you need about 15k chips.
7h\2h shoves, you call, you win and double to 3k.
7h\2h shoves, you call, you win to double to 6k.
7h\2h shoves, you call... well if you win here you're winning 3/3 when you should only win 2/3. But you win.
7h\2h shoves, you call. Winning 4/4. How greedy are you to expect that? But you win and now have enough to cash.
of you winning 4 times in a row with those hands? 16% That's worse than one out of 6 games.
And getting it in with A/K vs 7/2 is a dream scenario. If you expect to get it in good that many times in a row, you have issues.