Or maybe my explanation is wrong. I just often note some writing" verb +to +verb+ing" such as in this way. I analyze the second verb's meaning in that situation and suppose it is a gerund.
Maybe "to+verb+ing"as a gerund is only allowed by following some specific verbs such as "look forward" or something else. Honestly, I feel a lit bit confused so that I leave THIS PROBLEM for you and expect you to find a solution:)
你看见的那些都是固定的搭配, to 在这里是介词, 所以要跟名词性的东西。
如:
look forward to,
get down to,
devote oneself to
object to
lead to
give rise to
make contributions to
get used to
be subject to
due to
thank to
pay attention to
when it comes to
access to
......