<p>Let's not forget that
the listed masses are notoriously unreliable. We also don't know for certain that Trespasser was more durable than any of the other early Kaiju, because we don't know the yields of the weapons used to defeat each one.
</p><p>If, however, we do assume that Trespasser was tougher, it is entirely reasonable to accept Glitch's explanation that since he was the first, he would be designed to be durable so as to provide maximum intelligence to the Precursors.
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