Strong verbs tend to be really old! They've been part of English (and middle English, and old English, and anglo-frisian, and West Germanic, and...) for a long time!
When we invent new verbs, we tend to make 'em simple.
(No one's out here claiming the past participle of "milkshake duck" is something wild like "milkshake dacken," you know?)
anyway, the point is that these strong verbs have a history. a heritage. They've got a story.
SINK comes to us from Old English SINCAN (...SANC, SUNCEN)
DRINK comes from DRINCAN (...DRANC, DRUNCEN)
STINK from STINCAN, WRING from WRINGAN,
RISE from RISAN (...RAS, RISEN), FALL from FEALLAN (...FEOLL, FEALLEN), SIT from SITTAN (...SÆT, SETEN), LIE from LICGAN (..LÆG, LEGEN), DRIVE from DRIFAN (...DRAF, DRIFEN), GROW from GROWAN (...GREOW, GROWEN) etc, etc
you can start to see some patterns!
So where we today might -IFY a verb if we wanted to signal it was causative, the languages Modern English descended from had their own signals
and long story short (too late?): two of those signals were 1.) Changing vowel sounds and 2.) Making the new verb weak instead of strong
and without getting too deep in the weeds of historical linguistics here, both the original verbs and the derived causative verbs slowly evolved into Modern English
Language changes in a lot of ways, and those words don't always mean exactly the same thing they used to...
But they're recognisable! There are patterns!
Looking again at our strong verb list above, we've got some familiar friends
what do you do if you want something to RISE? You RAISE (RAISED—RAISED) it.
What if you want to cause a tree to FALL? You FELL (FELLED—FELLED) it!
Here's one that's been fossilized in legal language: you might say that an apple HUNG from a tree, but the state HANGED a man
(HANG—HANGED—HANGED)
(I made a typo here, SIT should be SIT—SAT—SAT)
(it's not a great spot to have made a typo, because I'm about to break a pattern a little bit, but stick with me)
You SIT on the chair. Yesterday you SAT there, too . You have SAT there every day for a long time.
You have an apple. You SET it on the chair. You SET it there yesterday, too. You have SET it there every day for a long time.
regular: SIT—SAT—SAT
causative: SET—SET—SET
same thing with LIE!
You LIE on the bed. You LAY there yesterday, too. You've LAIN there every day for a long time.
You LAY the blanket on the bed. You LAID it there yesterday, too. You've LAID it there every day for a long time.
regular: LIE—LAY—LAIN
causative LAY—LAID—LAID
okay, so here's where it gets really fun
like I said earlier, language changes over time, and the modern words that descended from stuff like WRINGAN don't always have a one-to-one meaning correlation with their ancestors
but we've got patterns to look at, and they're gonna help us out here
you might WRING a washcloth, but if you were mad you could WRENCH it out if someone else's hands
you trash can could STINK. You might even say it's had a STENCH.
sometimes one word, or the other, didn't make it all the way to the future when we are today
remember SINK—SANK—SUNK?
well, once upon a time, if you were to make something SINK, you would... SENCH it