German resistance may have had something to do with that, KG Walther may have only been an ad-hoc amalgamation of KGs including such dubiously reliable units as16th penal battalion, but it also included FJ and a regimental sized KG from IInd SS panzer corps. Examination of a decent map also reveals that the terrain between the border and Eindhoven is not very conducive to a rapid advance (unless you swing well to the left but that leaves the highway in German hands).
Waiting for the bridging column to come up and then building the bridge. The canal was a significant obstacle.
The Grenadier Guards group (2nd GG tank battalion and 3rd GG infantry battalion) stopped at nightfall and the following day fought all the way to Elst before being stopped by German resistance. Grabner gets slated for charging over Arnhem bridge, how about those stupid Brits making an armoured night attack against unreconnoitered positions with no artillery support on a single tank front? It is of course _possible_ that a night attack may have taken Else, but it was still only halfway to Arnhem, and the Germans had already recaptured the bridge there. I guess this is one move which we'll never really know the outcome for.
staying in Lent? ..there were
Just the infantry, anti-tank guns, light armour (if Jagdpz IVs count as 'light'

and artillery which had been ferried across the Rhine over the previous days, plus the heavy company of 9th SS PzAA which was still holding the southern end of the bridge and moved to Elst once KG Knaust had captured it.
See 'It Never Snows in September' by Kerhsaw, gives a very detailed breakdown of the German forces available throughout the campaign. It was of course ironic that just as Nijmegen bridge was being captured, the Germans had bulldozed their way across Arnhem bridge - Frosts men were doomed when Nijmegen bridge was not siezed on the first day. The eventual capture of Nijmegen bridge was far too late to help them, and even if the Brits had taken Elst in a foolhardy night attack, there were plenty of places further up the road for 506th SchwPzAbt to park their King Tigers.
The only solution to the tactical problem of the elevated highway was the flanking manouvre across the polder subsequently executed on the 22nd, headlong tank attacks weren't going anywhere - as the Germans found to their cost in their attempts to counerattack back down the road. Harmel (always one for a pithy quote) said 'This fighting (on the Island) tore the heart out of 10th SS Panzer Division'. 10th SS was utterly wrecked by its attempt to hold the highway and was unable to participate in the Bulge, whereas the partially rebuilt 9th SS was, albeit as a weak second wave formation.
Cheers