This encounter was incredible because Malfurion had seen Broxigar in his dream, so he immediately realized that Broxigar might be able to help him solve his current predicament.
Thus, he planned to find a way to save Broxigar. Although he couldn't explain the cause and effect, Tyrande chose to believe him without reservation. In the end, she even took the initiative to find Illidan to help save Broxigar.
After saving Broxigar, Malfurion brought him to meet his mentor, the demigod Cenarius.
The moment Cenarius saw Broxigar, he directly judged that Broxigar was not from this world and said that he didn't belong to this time and space.
Moreover… there was another person who didn't belong to this time and space…
Under Cenarius's lead, they meet another chosen one. It was Rhonin, who was under house arrest.