Wikipedia explains the tradition:
The taqiyah (also spelt "tagiyah"; Arabic: طاقية / ALA-LC: ṭāqīyah) is a short, rounded cap worn by some observant Muslim men. [...] In the United States and Britain, many Muslim merchants sell the prayer cap under the name kufi. [...] For men, it is mustahabb, which means 'commendable' or 'seeking the love of God', to cover the head during prayer.
His trip is, afterall, to the Middle East and not just Israel. If not, why not?