Ilusionado is a rich Spanish word that can mean 'hopeful' or 'excited,' but also carries a nuance of being 'deluded' or 'under an illusion.'
In this song, the singer uses it to express his deep emotional investment, asking, "¿Por qué jugar de esta manera si yo estaba ilusionado?" (Why play this way if I was hopeful/deluded?). It perfectly captures the pain of having his hopes dashed, implying he was perhaps too optimistic or even fooled by the situation.
Have you ever been completely swept away by love, only to have it end abruptly, leaving you with a million questions? That's exactly where El Bebeto is in "¿Por Qué Dejaste Que Te Amara?" [Why Did You Let Me Love You?]. He's looking back at a love that felt destined, singing, "Tenías que aparecer, tenía que suceder" [You had to appear, it had to happen]. He gave his all, loving without question, only to be told "adiós" [goodbye] after experiencing so much love.
He's genuinely confused and hurt, repeatedly asking, "Por qué dejaste que te amara, como nunca había amado?" [Why did you let me love you, like I had never loved before?]. He can't understand why she let him get so close, sleep in her arms, and make love to her if she was just going to leave. He even asks, "Por qué no me corriste de tu vida cuando miraste mis ojos y me sentiste enamorado?" [Why didn't you push me out of your life when you looked into my eyes and felt me in love?]. It's a raw and honest plea from someone who feels completely blindsided and wishes he had been warned before falling so deeply.