Boost criteria?

Hi,

I’ve been wondering, is there any reason why you gain boosts on some matches and not on others? Sort of, if I win x battles consecutively, or if I play stronger opponents, or if I play on tournaments a lot, am I more likely to win a boost? I’ve been curious about it for quite a long time.

I’m pretty sure it’s just a random drop.
Like you get 5% chance after every fight.