The only explanation is that frog attained jhana. It’s pretty interesting if jhana would be possible for animals :)
Three potential explanations:
- Frog attained jhana
- Frog attained samadhi (which is not regular state of mind that you can set yourself up thru emotions, but doubt as this takes one effort)
- Frog was at the end of bhava and things happen because of good kamma of the frog.
I think Yash misintepreting emotions (vedana) with mental state (citta)
There was other sutta when dying monk was taught by Ananda metta meditation, Buddha “scolded” Ananda that he should teach him Dhamma (Anicca, Dukkha and Anatta) so they come to his realm of devas to teach him Dhamma. Seems if the is strong samadhi and proper citta it may influence rebirth to some extent but I would not say it’s bulletproof method. It may work for certain individuals only.
The point is that Metta worked as gateway to jhana, you can not have metta without jhana to be honest the frog example is really interesting.