They’re getting desperate.
The GOP has been tweaking the delegate rules for many states since 2012 in order to prevent a non establishment or tea party candidate from rising. It backfired on them because Trump is way more popular than the others. If he bring votes in similar to his poll numbers, the GOPe will be hurting.
For this same reason, Cruz would have a hard time winning the nomination even if Trump dropped out today. The rules are set to kill candidates like Cruz.