In general Jews desired to falsify Christianity, and being able to point to Jesus's non-resurrected body would have seemed the most obvious and simple way to do this.1
But wait, maybe the Jews knew or believed that early Christians preached a non-physical resurrection (which would not be falsfied by showing the corpse).
“Jews saw reason to refrain from checking the tomb, feeling that they would contract 'corpse-impurity' upon entering into a tomb with a corpse.”
By way of response, however,…
• …contracting ritual impurity was common and not that big of a deal. It especially was not that big of a deal relative to their strong will to falsify Christianity [Forthcoming].1
• …scholars regularly echo the sentiment of Keener and Althaus here.2
• …gentile servants/allies were also available to check.
• …it was sufficient to simply open the tomb up (to look without entering).
• …it was sufficient to simply point to Jesus's known tomb.
• …the bones would be seen anyways in 6-12 months.3
• Leen Ritmeyer: “Over 1,000 tombs have been studied around Jerusalem, and we know now that the first stage in tomb construction is the cutting out of a single chamber with benches arranged along the three sides, leaving a pit in the middle, so that the workmen could stand upright while working. A tomb could be left like this for a while, until the other chambers were added.” [https://blogs.thegospelcoalition.org/justintaylor/2008/07/24/what-did-jesus-tomb-look-like-interview/]