@Krackers The emperor doesn't like his first son because (if I remember correctly) the empress he had married to get to the thrown was strong in power and thus the emperor destroyed the empress's power and then disposed of her. He later had a child with a woman he liked and 2nd prince was born. So he wants to give the thrown to his second son.
Then the next strongest family with power was the Jun family. So he planned to have his second son marry the MC, take their power and then destroy them. But then that student of the great doctor of the strongest medical sect, fell for 2nd prince and around that time it was discovered that MC doesn't have any sprit, so they decided to dispose of her and choose the medical student.