It's not surprising. For many parents, lack of sleep is the worst part of having a baby, and 'controlled crying' is a way of 'teaching' babies to go to sleep at bedtime and sleep through the night. 'Controlled crying' means settling your baby into her cot at the time you've decided and then leaving her, crying or not, checking she's OK at regular and increasingly widely-spaced intervals (such as every five, then ten, then 15 minutes), but not picking her up again.
Some babies don't cry, or only for a minute; they are happy to settle and don't need controlling. But some cry a lot, night after night. Left crying for long enough, they all eventually stop, not because they have learned to go to sleep happily alone (young babies brains aren't up for that kind of learning) but because they're exhausted and have given up hope of help.
Brain development isn't like physical growth - a matter of genetics, age and nutrition. It depends on babies' relationships and experiences with parents or other main carers. Parents literally build infant brains, and responding or not responding to crying is an important part of that.
Crying is communication: babies' only way of signalling discomfort or distress. They can't restore their own equilibrium, so it's the adult's job to do it for them. Being left crying hard is stressful. If acute stress continues, a hormonal chain reaction starts, stimulating the adrenal glands into releasing the 'stress hormone' cortisol. Long, continued crying can bathe the baby's brain in damaging amounts of cortisol, and if that happens, often the brain's hard-wiring may be permanently set on hypersensitive, so that the baby reacts to minor stress with major anxiety for the rest of her life.
Responding to the crying counteracts the cortisol by stimulating 'comfort hormones' (notably endorphins). If that is what usually happens, the brain will become hard-wired to release endorphins whenever cortisol levels soar, enabling the toddler to soothe herself and building lifelong resilience to help her cope with life's stresses.
No controlled crying doesn't mean no routines - only no routines that distress a baby. Routines arrived at together may help you both to feel confident and safe. A baby's behaviour is by far your best guide to caring for her, so watch the baby, not the clock.
