I wouldn't really say nothing, Ragans was essentially gifted in retrospect, but the price was Aroldis Chapman whom they shrewdly signed coming off a down season in his last Yankees year. He was elite for them and they capitalized by sending him to the contending Rangers, who then would go on to win the WS in some part thanks to his contributions. That's just smart business all around by the Royals.
For Erceg, they approached a non contending A's team and sent a couple of 40-45 FV guys in return for him. Standard RP business, sometimes the prospects work and sometimes they don't. Good evaluation on their end to ensure they didn't lose anyone they would regret, although it's probably too early to make such claims.
Like I said for Garcia, he was a heralded prospect who contributed in other ways while showing promise under the hood. What you might see as mediocre MiLB performance is a guy that was always young for the level staying afloat with solid K/BB, excellent baserunning and defense, and probably some encouraging EV numbers that they were privvy to. He was still a 1-2 win player in his first two MLB seasons at ages 23 and 24 with promise, not a guy you give up on quickly.