I am writing something at the moment and have three quotes from three pilgrims from three different centuries as follows.
Hyecho (704–787 CE) makes the following brief comments on the state of Kapilavastu:
《遊方記抄》卷1：「迦毘耶羅國。即佛本生城。無憂樹見在。彼城已廢。有塔無僧。亦無百姓。... 林木荒多。道路足賊。往彼禮拜者。甚難方迷。」(CBETA, T51, no. 2089, p. 976, a2-5)
The country of Kapilavastu. It is where the Buddha was originally born and the city [where he was raised]. The aśoka tree [under which the Buddha was born] is still extant. The city has been abadoned. There are stūpas, but no monks. There is also no populace. The forests are much neglected. The roads are full of bandits. Those going there to pay respects have much difficulty and lose their ways.
Xuanzang (602–664) in the previous century recorded his observations in more details as follows.
《大唐西域記》卷6：「劫比羅伐窣堵國，周四千餘里。空城十數，荒蕪已甚。王城頹圮，周量不詳。其內宮城周十四五里，壘甎而成，基跡峻固。空荒久遠，人里稀曠。無大君長，城各立主。土地良沃，稼穡時播。氣序無愆，風俗和暢。伽藍故基千有餘所，而宮城之側有一伽藍，僧徒三千餘人，習學小乘正量部教。天祠兩所，異道雜居。」(CBETA, T51, no. 2087, p. 900, c22-29)
The country of Kapilavastu is more than four-thousand li in circumference. There are tens of empty cities, truly abandoned and overgrown with weeds. The king's city is decrepit. The measurements for the circumference are unclear. Within there is the palace, fourteen or fifteen li in circumference built of layered bricks, the remains of the foundation tall and solid. They have long bee emptied and abandoned. The villages of the people are rare and scarce. There are great lords or chiefs and the cities individually elect their headmen. The land is fertile. Sowing or harvesting they are often seeding. The order of the seasons is without lapse. Their culture is gentle and kind. There are more than a thousand old foundations for temples, though on the side of the palace there is one temple with over three thousand monks who study the Hīnayāna Saṃmitīya-nikāya teachings. There are two Hindu sites and the different paths reside together.
Faxian (338-c423) has brief remarks as follows:
《高僧法顯傳》卷1：「從此東行減一由延到迦維羅衛城。城中都無王民甚丘荒。止有眾僧民戶數十家而已。」(CBETA, T51, no. 2085, p. 861, a22-24)
From here going east less than a yojana away one arrives at the city of Kapilavastu. Inside the city there is neither king nor citizens and it is quite desolate. There are only the monks and some tens of households.
Does anyone know why Kapilavastu fell into ruin? Any good reliable history resources to explain this? We know from at least one eyewitness account it was largely abandoned by the early 5th century.
I know Virudhaka is said to have wiped out the Sakya clan, but would that explain the desolate state of the whole realm after so many centuries as well?