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The 3 "C"s:
Cooling. How long was the scope outdoors? A 130mm triplet can sharpen optically over an hour or two after it's been brought out.
Collimation. Have you checked the collimation? Just because it's a triplet doesn't necessarily mean the scope is collimated. I use a "daytime star" to collimate my triplet refractor, i.e. the reflection of the sun off a Christmas tree ornament hung on a tree at least 100 meters away. I recommend green for visual acuity.
Conditions. Seeing can be broken down into two components: lateral motion and scintillation. Lateral motion won't influence the ability to see the E and F stars in the Trapezium (though I think it takes 32cm to see the G and H1 members, and perhaps a 15" to see the H2 and I components), but scintillation will blur the stars to the point where E and F are pretty much invisible. In average seeing, 15-20x per inch of aperture (77-102x) should be best to see them. In good seeing, 20-25x/inch of aperture (102-128x), and in exceptional seeing, 25-60x/inch (128x-307x). That last will be a rare night.
All 3 "C"s have to be right to see things at the limit of the scope, like some of the craterlets in the floor of Plato (most visible 1-2 days after the sun has appeared at Plato).
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