"If G-d [The Creator] chose Yisrael, therefore, He must have found unique merit in them

Moses gives two reasons for G-d's choice of Yisrael:

He found them worthy of His love, and because of His oath to their Patriarchs.

The reason for His love is not given, but it may be because He knew Yisrael's faithfulness would be unswerving." - Ramban

"One who serves out of love is ready to make great sacrifices for the object of His affection" - Rashi/Rambam

"Meditate on G-d's great and wondrous deeds and creations through Torah and seek His incomparable and infinite wisdom, this will lead to love and appreciation of Him and a desire to know Him more." - based on Rambam

For centuries, the Jewish people made extraordinary sacrifices to remain faithful to the Creator.

That unswerving loyalty reveals a deep love, sometimes consciously felt, and sometimes hidden beneath faith, awe, and commitment.

"It is natural to choose a friend that will remain loyal no matter how great the difficulty" - Ramban